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How to Make Chocolate Mousse (Science of Stabilizing Foams)
A good chocolate mousse is smooth, airy, chocolatey, and melts in your mouth. It definitely isn’t gritty, watery, dense, or even clumpy.
Making chocolate mousse is all about creating that light foamy texture, without having it collapse on you. And luckily, using science, we know a thing or two about stabilizing foams. In a chocolate mousse, the chocolate itself has a crucial role in stabilizing the texture. But, don’t underestimate the power of eggs, cream, and even gelatin in a good mousse.
- Step 1: Melting the chocolate
- Step 2: Incorporating air
- Step 3: Carefully mix it all together
- Step 4: Cooling down
- Chocolate helps to stabilize the mousse
- Gelatin forms a gel to stabilize air bubbles.
- Whipped cream adds air and water
- Eggs add and stabilize air bubbles
- Heat can pasteurize the eggs
- Do the eggs need to be split?
- Can you make a chocolate mousse without eggs?
- Sugar adds sweetness
Chocolate mousse is a foam
One of the most important aspects to keep in mind while making a chocolate mousse is that it is a foam. That is, chocolate mousse is made up of a semi-solid continuous phase of chocolate and other ingredients, with tiny air bubbles dispersed all throughout. Without these air bubbles it wouldn’t be a mousse. It would just be a ganache, or maybe a pudding. When making a mousse forming and stabilizing the foam is the crux. Once you have that under control, you can make a wide range of chocolate mousses.
Making chocolate mousse is about:
- creating enough air bubbles
- making sure they don’t disappear again later in the process!
How to make chocolate mousse
To make this foam, there are a few common steps to take, though not always in the same order:
- Melt chocolate
- Whisk ingredients to incorporate air
- Carefully mix ingredients together
- Cool the mousse to stabilize
Step 1: Melting the chocolate
Chocolate is solid at room temperature. This is great, as we’ll see later, for stabilizing your mousse. However, it is less ideal when making the mousse. There’s no way to evenly incorporate solid chocolate into a mousse. As such, most recipes start by melting chocolate.
Chocolate is completely melted at 45°C (113°F) so you don’t need very high temperatures. As a matter of fact, it’s best not to heat it up more than necessary, since chocolate can burn when it gets too hot.
Once molten, it’s easy to mix chocolate with other components. However, do keep in mind that chocolate will start to solidify as soon as it starts cooling down, especially once it starts getting below 30°C (86°F). This may happen slowly at first, but, if you add cold ingredients, it can happen quite rapidly.
Use a microwave or au bain marie
We prefer melting chocolate in the microwave. It’s very effective and only takes a couple of minutes, depending on the amount of chocolate you’re trying to melt. Remember that a microwave has hot and cold spots. As such, part of the chocolate may burn before other parts have melted. You can overcome this easily by stirring the chocolate every 30s or so, before placing it back in the microwave.
The other very commonly advised method, is to melt chocolate au bain marie. Since chocolate is prone to burning, it’s best not to melt it above a direct heat source. Instead, in au bain marie, you place a bowl of chocolate on top of a pot of boiling water. As such, it won’t get warmer than 100°C (212°F) and you won’t risk burned chocolate.
Step 2: Incorporating air
This is probably the most crucial step and it’s what really defines the consistency of your mousse: adding air bubbles into the mouse. There are roughly two ways to do so:
- Whisk an ingredient that’s good at holding onto air itself, such as heavy cream or eggs.
- Whip the chocolate mousse as it’s cooling down. It will hold onto itself, though not create as light and airy a texture as the first method generally does.
Almost all recipes use the first method, but we did test one using the second method further down.
By whisking, or intensely mixing something you’re giving air from the environment a chance to sit within what it is that you’re mixing. If that ingredient can then stabilize the air bubbles that are formed within, you’re creating a foam. A lot of ingredients cannot form such a foam. Just try whisking water. No matter how long you whisk it, the air will disappear from it almost immediately. Instead, you need ingredients such as fat or proteins to be present to help hold onto those air bubbles, as we’ll find when looking at eggs and cream in closer detail.
Keep in mind that this is often the only step that adds air to the chocolate mousse. All other steps will only reduce the amount of air. The mousse is never going to get any lighter than what you make it at this point.
Step 3: Carefully mix it all together
At some point, you’ll need to mix the light and airy foam with other ingredients, such as the chocolate. These other ingredients tend to be heavy and dense and will partially collapse your foam again. So, from this point onwards it’s all about careful mixing and folding to try and reduce the amount of inadvertent air loss as much as possible
It’s hard to mix two components that have very different densities. As such, don’t try adding all of them together in one go. Instead, slowly bring the two densities closer by first incorporating a little bit of the light foam to the dense ingredients. This will lighten up the dense ingredients. Adding the next portions will become progressively easier as the densities become more similar. This is the best way to prevent losing a lot of air, which you’ll inadvertently do when adding it all together in one go.
Keep in mind that mixing cold ingredients with warm melted chocolate will cause the chocolate to start to set, making it harder to evenly mix in the other ingredients.
Step 4: Cooling down
Think your chocolate mousse is still very delicate after mixing everything together? Well, it probably is. The mousse gets some of its stability from the chocolate that sets (which we’ll discuss in more detail next). As such, this last chill step is crucial. As the mousse cools down in the fridge, it becomes firmer and less delicate.
The basic ingredients of chocolate mousse
You can make a chocolate mousse with as little as two ingredients: just chocolate and water. However, most recipes will at least call for some cream or eggs. Let’s have a look at the role of all of these ingredients.
Chocolate helps to stabilize the mousse
Whereas a lot of foams are stabilized by heat (think meringues, cakes), the opposite is true for a mousse. It becomes more stable once cooled down and that’s because of the presence of chocolate. Recall that chocolate is solid at room temperature. As such, when a mousse cools down, the chocolate again turns solid (melting & solidification are both reversible processes). A solid material is a lot better at holding on to air bubbles than a liquid is. The air bubbles are simply trapped inside, they can’t go anywhere.
Gelatin forms a gel to stabilize air bubbles.
Gelatin is quite a unique ingredient. It’s a mix of broken down proteins and happens to be able to form delicate, wobbly gel-like textures. In a chocolate mousse, this gel-like texture helps to stabilize the mousse. The gel is more solid than a liquid would be. As such, it again is better at holding onto air bubbles and preventing them from escaping. Since the gel is still soft and literally melts in your mouth, it still makes for a soft, and smooth texture.
Can you make a chocolate mousse without gelatin?
Short answer: yes, you can. Gelatin does help with the longer-term stability of a mousse. Also, if you’re making a mousse that doesn’t contain chocolate (e.g. a strawberry mousse), you probably need gelatin, or an equivalent ingredient to ensure the mousse remains stable over time since you lack the stabilizing feature from the chocolate itself.
Whipped cream adds air and water
Heavy whipping cream is great at foaming, thanks to its high fat content. The fat particles in the cream will surround the air bubbles and ensure a light foam is formed. However, whipped cream is not very stable. If left alone, whipped cream will start to collapse in a matter of hours, even faster at higher temperatures. It’s why heavy cream is great for adding air but needs the help of other ingredients to make sure that light and air chocolate mousse doesn’t start collapsing right after you make it.
Don’t whip it too much
You have to mix the whipped cream (and/or eggs) with the other liquid ingredients of the mousse. This can become quite challenging if the whipped cream is whipped up into very hard peaks, close to becoming butter. Instead, you want the whipped cream to be light and airy, but still have quite soft peaks.
Water lightens the mousse
Chocolate does not contain any water. As a matter of fact, if chocolate comes into contact with water it seizes up and only when you add enough water will it become a manageable texture again. Cream contains about 80% water, so adds a significant amount of water to the mousse (as do eggs by the way). This water is necessary to lighten up the mousse and make it capable of holding onto that air. Just fat would make for a very heavy and dense dessert.
Eggs add and stabilize air bubbles
Eggs are one of the best suited ingredients for making a foam. The protein in especially the egg whites can hold onto air bubbles very well. These proteins have parts that prefer to be in water and parts that do not. This way, parts of a protein will want to sit in the water, whereas the other part prefers to sit in the air bubble. By arranging themselves around these air bubbles, they prevent air bubbles from escaping.
Heat can pasteurize the eggs
A lot of chocolate mousse recipes use raw eggs. Whereas this may be fine for a lot of people, not everyone feels comfortable doing so. However, there’s a way to use eggs, without them being completely raw. Instead of whisking eggs at room temperature, you whisk eggs, with some sugar, light and airy au bain marie, that is, above some boiling water (you’re essentially making Swiss meringue but with the egg yolk included). The water will heat the eggs and pasteurize them, and, as a great additional benefit also help them become even more light and airy!
Do the eggs need to be split?
That depends on the recipe. Some recipes, such as the one below, call for whole eggs, others split the eggs and might not use the whole egg. A major reason for splitting the eggs is that egg whites can foam up a lot better than egg whites + egg yolks can. Egg yolks even making it a lot harder for egg whites to foam up. So, by whisking them up separately, an airier mixture can be made that is then gently folded together with the other ingredients.
Can you make a chocolate mousse without eggs?
Yes, you can, as we do in the mousse for this Italian cake.
Sugar adds sweetness
Last, but not least, a common ingredient in mousses is sugar. Chocolate itself will contain a good amount of sugar, especially milk and white chocolate, but a mousse often contains a little extra. The sugar sweetens the mousse, but also contributes to its texture, lightening things up. Sugar also helps with aeration since both eggs and heavy cream benefit from containing some sugar when they’re whipped up. The sugar helps stabilize the foams, making it a little harder for the air bubbles to escape.
The proof is in the
To show some of the effects of the different ingredients in a chocolate mousse, we made three different chocolate mousse recipes:
- A mousse made of just water and chocolate, aerated by whisking the mixture when it was just starting to set, but still liquid enough to be aerated.
- A mousse made with just cream and chocolate, made in the same way as mousse no. 1
- The mousse given in the recipe below, containing eggs and cream.
Whereas all three were nice to eat (it still is a lot of chocolate…) the third one was our favorite. It was the lightest and airiest of all. All those eggs and that cream incorporated a lot of air. Recipe no. 2 was a little too dense, we probably added too much chocolate, and not enough cream. The chocolate pushed out a lot of the air again, making a ganache. However, we’re pretty confident this would have made a nice mousse with more cream. Recipe no. 1, with just chocolate and water, was probably the most surprising. It definitely made a mousse. But, of course, it wasn’t as rich as creamy, it was almost a little watery. But, it was a great light way of adding chocolate and even though we didn’t like it as much by itself, it would work great in a dessert with other components where you don’t want a rich chocolate mousse weighing everything down.
Hi! Do you think this recipe would hold up as a cake filling between layered cakes?
Hi Janel! Thanks for coming by. Once the mousse has set it becomes quite firm so I think it should well hold between two layers, although I never tried it myself. Don’t build the cake too high though (I would guess three thin cake layers with mousse should work) and make sure the mousse has properly chilled before building the cake. Chilling the mousse is super important to let the chocolate set and the mousse firm up.
Hi planning to do master chefs version will it be firm enough for my 3d dog mousse mould?
Hi Sydney, not too sure what type of mould you have. If you’re planning to unmold it, that might become tricky since it’s a little delicate. If you’re planning to eat from the mould directly it should be fine!
Could I also make the Masterchef version with white chocolate or would I need to alter the ratios?
I haven’t tried it with white chocolate, but I think you can definitely give it a try. Keep in mind that it will be sweeter for sure. The texture may change a little as well since the dark part of milk and dark chocolate does thicken the mousse more. But, I would suggest you just give it a try. I’m pretty sure it will still taste you, you might just need to optimize it a little by potentially taking out some of the sugar and maybe reducing the amount of a milk a little (I’d suggest starting with a 25% reduction).
Reposting my question as there was a grammatical error in my last post:
In Mary Berry’s recipe instructions, step 3 reads: “Mix the egg yolks through the egg yolk.” What does this mean? I don’t understand it and its connection to the next part of the step: “It will initially become very thick. If it firms up too much very gently re-heat it slightly, you don’t want to re-heat too much or the egg yolk will cook.”
Thank you for catching that! I updated the recipe just now. Instead of mixing the egg yolks with egg yolks you’re supposed to mix them with the warm (but not hot) molten chocolate. Hope the new version makes sense, enjoy!