How to make cold chocolate shake: 4% milk fat, 30% cacao butter content & some chocolate hacks

Ruby Islam, head chef, Manam Chocolate. (Photo credit: Nishant Ratnakar)

There are of course many versions of cold chocolate, from the malt-based chocolate milk drinks for children to those inspired by international food trends. But if, like this writer, you've ever felt let down by what arrives at the table when you order / cook-up a cold chocolate drink - or as it is also called, cold drinking chocolate or cold hot chocolate - read on for Chef Ruby Islam's tips to make a good one and the science of how it works. Spoiler alert: She recommends making hot chocolate first, cooling it for several hours and then re-blending it before serving / savouring. Edited excerpts:

So many questions come to mind: Let's start with what is a good cold chocolate? And does it always have to be thick?

For me, an ideal cold chocolate is something that is drinkable, is sippable, but it coats your palate, coats your mouth, it coats your tongue. So you want something which is chilled - and I get quite technical with this, where I want the beverage to be between 6 and 7°C. That's a nice cold chocolate. And if you want to go further (colder drink), then you can pour it over a cube of ice. But I love to have it be refreshing and, at the same time, I want associate it to a liquid form of chocolate. So I want it to coat my mouth, I want it to coat the tongue and I want it - in the chocolate world, we would say a long-lasting finish - to have a long finish.

What's a reliable hack to get this long finish?

One of your questions was with regards to making chocolate drinks with cocoa powder or syrup or chocolate - which is it? It is definitely chocolate itself, because the coating comes with a cacao butter that's in pure couvertures (couverture is chocolate with a higher percentage of cocoa butter - the natural fat in cacao beans - than baking chocolate and commercial chocolate bars).

When you make a cold chocolate with melted chocolate - starting with making hot chocolate, and then cooling it down - you're going to get the best results.

A cold chocolate is great when the entire suspension of the chocolate has homogenized in your milk, because they (the fats) come from two different sources (the cocoa butter from quality chocolate and the milk fat). They really need to bind together, which means that you heat it (the mixture) and then you cool it down and blend it or emulsify it. That way, you're using a really good quality chocolate in a good quantity, but at the same time you feel the consistency in the mouth because you've added that step of emulsification.

So one needs to make a good hot chocolate first, and then chill it to 6-7 degrees to get a good cold chocolate? What does it mean to homogenize it, and does it stay that way after the drink has been sitting in the fridge for a few hours?

When it comes to a cold chocolate - starting off with a hot chocolate - there is a method. You start by heating your milk towards boiling temperature, which is about 98.5 degrees Celsius. Then you add in semi-melted chocolate, which could be anywhere between 36 to 45 degrees. And on a very low flame, you cook it to a point where it's simmering. Now, this allows all the fat of the chocolate to sort of come out and mix into the milk.

I've done so many experiments with the kind of milk that I use: my friends would say that of course you're going to pick the milk with a higher fat percent. But on the contrary, I pick up 4 percent fat (milk) - it has milk solids at about 8.6 percent - as opposed to picking a milk with the highest fat, which in parts of our country is close to 7-7.2 percent fat. I don't want 7-7.2 percent (milk) fat because when you let chocolate (the cooked chocolate drink) settle overnight to bring down the temperatures, the fat sort of creates a layer on top and that's not something that you want. It's really about balancing the fat in both the milk, and the chocolate.

I start by cooking it (the milk and chocolate mix) very slowly. The colour brightens up as every part of the chocolate melts into the base of the milk. You'll actually start seeing the colour of it change - it becomes perkier, it becomes brown. It also shows the strength or the fullness of the chocolate. And then you start seeing a shine. And this is something that I always tell my team: lookout for the fat, which means lookout for the shine. If your product is shiny, then you know that you haven't split it. You've actually very slowly let it (the chocolate) melt and mix into the base mixture. And when you have when you have achieved that, you then have to emulsify it using a hand blender.

When you say waiting for a shine to appear, what does that look like? Is it like specks of fat on top of your mixture of chocolate and milk? And have you added sugar in it at this point or is it just chocolate and milk?

It's just chocolate. And no (specks), the entire mixture is really smooth and shiny. One of the things that you work it with is a whisk. You constantly want to keep stirring it (the mix of chocolate and milk that is simmering slowly at this point). I like to use a whisk as opposed to a spatula because then it just allows a lot of mixing with that tool; it's a really smooth, glossy, shiny finish. It's not in parts, it's not in specks. After you've slowly cooked the chocolate (and milk mixture) and you've mixed it with a whisk constantly, it even becomes more emulsified or brighter or shinier when you use a stick blender or an emulsion blender.

So you use a hand blender or a mixer that can handle liquids hot or is it okay to wait for the milk-and-chocolate mix to cool a little?

After you finish the whisking, when you're happy with the consistency, then you take it off the flame or off the induction and then you immerse an emulsion blender. (Blending it while) hot is good. Then I let it mature in the fridge for about 12 hours and that brings down the temperature to 6 to 7 degrees. The time that I want to serve it, I would emulsion-blend it again.

Because it separates a bit in the fridge?

Yes, because the chocolate is slightly heavier. The cacao solids are heavier than the milk, right? So even in spite of you having made a really smooth mixture with your shaft or emulsion blender, in the fridge somewhere, there's a light bit of settling. So you blend it again and then you drink it or you pour it over ice and then enjoy it.

This may be tedious process but if it gives you this really nice, long-lasting finish and it coats your mouth, you know that the fat is really holding up.

Do you have a point of view on really thick versus other consistencies of cold chocolate? And would you advise using thickeners like egg yolks or cornstarch?

This (thick shake versus other consistencies) is such a controversial question for me. When I started working with hot chocolate and cold chocolate, everybody would use their benchmark of a really thick, almost gelatinous consistency of both hot and cold chocolate. Over time, I realized that this is something that used to be a reference (point) of a Belgium or a Swiss or a French maker. I want(ed) to see what this consistency is. And I've travelled all across to find that it is not a gluggy mass. It's something that is extremely drinkable. You can sip on it and enjoy, like you're enjoying a craft coffee. And that's exactly the way I like it as well.

I like to drink my hot chocolate or cold chocolate and I want to have a guilt-free experience of having another cup in the same day, so I avoid adding high fat percentage cream or butters into my hot or cold chocolate, which quite a few recipes do.

Butters, cornstarch, egg yolks are sometimes used to thicken hot and cold chocolates, but if you're starting with a good chocolate that has 28-32 percent cacao butter, you can avoid the other thickeners. (Pictured here: Plant-based chocolate beverages at Manam Chocolate; photo courtesy: Manam/Lost & Hungry Studios)

What does the addition of butter do? If one is making the drink with couverture chocolate that already has a higher content of cacao butter in it and you put other things in, how does that change the result?

I don't like adding butters or cream at all, and I've seen a lot of recipes which actually suggest that.

You're saying adding butter is not a good idea, but it does thicken up chocolate for people that like butter in their chocolate drinks?

It does thicken it up, but my preference, and what I share with people also, is without that (added butter).

And do you suggest adding egg yolks? Some chefs recommend it for a custardy hot chocolate that's velvety and thick, but does it work for cold chocolate shakes - perhaps for a version like yours where you are cooking the chocolate and milk out before cooling it for a cold chocolate? And do you recommend adding salt?

I'd say the secret ingredient to desserts is always a fine quality salt. You need to pick your salt, and you need to choose it well to a point where it's not interfering with the flavour, nor is it giving your table salt impact which is very different in taste compared to something which is like a Malden Sea salt.

But the second secret ingredient to this entire mix is a fine flavoured chocolate. So I want to start my recipe with a percentage which works really well. If I want the chocolate to speak for itself, I would not need an egg yolk or any other thickening agent. Because the beauty of hot and cold chocolate, is that when you allow the mixture to cook well - at very low temperatures because you don't want the mixture to split, and I keep coming back to this thing that chocolate is a suspension and it needs to be emulsified in any other liquid - you don't need to add any other thickening agent, not even cornstarch or egg yolk.

So pick a chocolate which has a very strong intensity, but also look at the label for its fat percentage. Because in the formulation, the fat percentage of the chocolate will also allow you to take that decision of which one you want to use for a cold chocolate. And then you're working just around two fats: one is of the milk and one is of the chocolate itself.

So what percentage of fat are you looking for in the chocolate?

My favourite is a 70 percent chocolate. It's an average of 35 percent fat, 35 percent cacao solids, which gives you the flavour in the aroma and it's a 30 percent sugar for me that really balances it out right.

Different brands of 70 percent dark chocolate could have different ratios of cacao butter to solids, right? So roughly 30 percent cacao butter is what you're looking for?

Anywhere between 28 to 32 actually, but that's my favorite. I also work around 66 and 67 percent chocolate, because in some of the drinks I want to go slightly sweeter because that's also what we associate with cold chocolate. And then I like to level it up with ingredients like orange zest or vanilla or sea salt, chili, in some cases black pepper. I have a 66 percent Idukki which I use from Kerala beans and that has a very strong flavour note of raisins and candied fruit, so I love to pair that up with freshly ground black pepper.

Your sugar is essentially coming from the chocolate itself, then? Or are you adding sugar depending on how dark you're going with the chocolate?

It's just from the chocolate itself.

For somebody who wants less sugar or a sugar alternative like monk fruit sweetener or Stevia, is there a workable alternative, or do they not make for a great glass of cold chocolate?

Monk sugar does a good job - I like monk sugar in liquid form; it holds well. I also feel like fresh stevia leaves in a cold mint chocolate tastes very nice. So if you were to make a cold chocolate with mint leaf and then sweeten it with stevia, which is the leaf itself and not the powder, then it's a game changer.

So you add the fresh stevia leaf after you've cooked out your hot chocolate, or after you've cooled it overnight or for 12 hours, or after you've blended it again for serving?

You add it before you blend the (hot) chocolate drink before putting it into the fridge. And then the next morning, you can strain it out and blend it again and have the drink.

Monk fruit is quite nice. That comes in a powdered form.

Of course, if people want to go sugar-free because of GI (glycaemic index), then they could use these options. But if they're OK with an alternative, I think maple syrup makes for a very, very nice, rounded flavour. Then you would use a much darker chocolate and then use maple syrup to sweeten it. You can go up to as dark as a 90-95 percent.

Does the milk not split when you have very dark chocolate?

Not really. Everything comes down to formulation, even when it comes to cold chocolate.

How do you feel about these slushies - chocolate drinks made with lots of ice in the blender?

I'm actually going to say that it has its own use case. When you're out in the sun at 50 degrees and it's really hot, you want to drink something which is refreshing. It gives you that antioxidant hit. Cacao is a super food. So even if it means that you're having a dark cold chocolate which is rundown with a lot of ice, there's merit in it. During that moment of heat, you don't want to have something that's really heavy. So I'm not really going to diss it, because there are moments where when I want that. But it's not my ideal form for consumption, for sure.

The chocolate you mentioned is the most important ingredient in all of this. So what are you looking for in a chocolate - is there a particular processing method you prefer, like Dutch processing? How do you make a choice between which is a good bean for the kind of cold chocolate that you want?

Hundred percent. When you're drinking a cold chocolate, you don't want the flavour of milk to stay in your mouth, you want the flavour of the chocolate to stand out. I prefer a cacao that is a lot more a fruity as opposed to having something which is a lot more rounded off in terms of its cacao powder or dark sugars or big brownie taste profiles because when you go really high on the roast of the bean, it gives you a more of an espresso taste. And in milk, I think that's something that is not very exciting because you still can taste the milk at the end of the day. It's also like your mind is telling you that you are having cold coffee, because it has that espresso note along with milk itself.

I choose the kind of milk that I have, which is not going to leave a note of the milk powder in your mouth or the taste of the milk itself in your mouth. And I would prefer chocolate made from an origin that's a lot more acidic and fruitier. Like Peruvian origin or I like a origin of a Madagascar chocolate and West Godavari, definitely. They have a fruity under note (which reinforces the sweetness we associate with chocolate). It almost makes you feel like you have had a citrus fruit after you consume that chocolate.

And what ratio of chocolate to milk do you suggest?

If you're using a 70 or 80 percent dark chocolate, (about 40-60 grams of chocolate in a 300-350 ml drink) is a good ratio. Let's say you come down as low as a 45 percent milk chocolate, then you would probably go to 60-40 (chocolate-to-milk ratio).

Black sesame praline latte hot chocolate at Manam Chocolate (Photo courtesy Lost & Hungry Studios via Manam)

Is there a thumb rule when you're adding infusions, flavourings, like you mentioned mint and stevia? What percentage of chocolate really works well for those kinds of experiments?

You mentioned that the sugar supports the idea that you're not having something bitter and reinforces some of that fruity flavour. Does it also help with the homogenization, among other things that give the hot / cold chocolate its texture and taste? And at what stage do you add the sugar?

Sugar has no role to play in emulsification or making the mixture a little more homogenized. The thing about sugar is that it melts into a liquid very comfortably. So sugar does not play too much of a role there, apart from the association of a hot or association of a cold chocolate that we've grown up having. Because our memories still go back to having a malt or a Bournvita, which is then iced down.

More importantly, it opens up the flavour note of the cacao itself.

If I talk to you about how a chocolate has fruity notes or red berry notes, I can't have you entirely experience that without adding the sugar in it, because then your mind will only register it as bitter or astringent, it won't associate to acidic or tart or fruity because that's also the nature of tart fruits. So that's one very important role that it plays.

The addition of it can happen when you heat up the liquid. And if you're using it in a liquid form, say for a maple syrup, you can add it to the liquid when it's completely cooled down as well or the milk base is cold.

Coming back to proportions, I think it's really about the kind of percentage of chocolate that you use. If we were to start with a baseline, say, I would encourage somebody to start with a 60% dark or a 55%... I like it to be much stronger because it really is about the cacao and not as much as the sugar because you're melting it into a base of milk itself, so my suggestion starts there, 45 percent (chocolate) and up only.

In terms of proportions, it really depends. It comes back down to the consistency, right? If you're going to take an average cup of a hot chocolate, which is anywhere between 300 and 350 milliliters, you at least want to have anywhere close to around 40 to 60 grams of chocolate going in there. That's just ballpark. It's going to be very different from a milk chocolate to a dark chocolate to even a white chocolate.

Is a low-calorie cold chocolate that's interesting even possible, then?

I have an option of 100% dark (at the beverage bar) which is very low on calories, which I do with an almond mylk. For somebody who would want an alternate sugar, we can do that. On the beverage bar menu, I also have the option to add a protein powder. So it really is a shift from what we've always perceived a cold chocolate to be and how often it can be consumed and with what level of guilt it can be consumed.

What does the addition of protein powder do to the mix - does it change the point at which the fats get homogenized or change something at a molecular level?

It actually makes it a little softer in the palate. It's very drinkable. It (protein powder) of course it has its own taste. You can't take away from that, but the consistency is rather smooth.

What kind of protein powder are you using - whey protein, pea protein, or does it not matter?

I currently use whey protein. I'm yet to find a pea protein which balances out its flavour note along with the cold chocolate; I'm doing some work on that also right now.

How does white chocolate work in a cold chocolate drink - when would you add that instead of dark chocolate?

White chocolate gives you the liberty to build up drinks with flavour notes that you would not be able to experiment with if, for example, I were to give you a 70 percent dark chocolate. If you said to me 'I love pistachio and matcha, can you add it to my chocolate drink?' I could add it, but it's not going to taste good (in dark chocolate). What white chocolate does is, it allows you that base to create different flavours, slightly more experimental flavors, which still give you the goodness of the cacao butter and the velvety soft feel of the cacao butter because that's where the melt-in-your-mouth experience comes. It's the butter that coats your palate. So in a white chocolate, that ability is there.