Chocolate mousse – stabilizing a foam

Chocolate mousse definitely is one of my favority desserts to eat. It’s a great combination of ‘heavy’ chocolate, with a light foam. Until not too long ago I had never been able to make a good chocolate mousse. They tended to sink in right after I made them, resulting in a liquidlike puddle of material or I never got the air in there at any point of time.

However, I never tried making a chocolate mousse using my KitchenAid stand mixer! Thus, last weekend I gave it another try again, hoping to get it just right.

Masterchef Australia chocolate mousse

My favorite tv show by far (actually one of the only tv shows I actually watch) is Masterchef Asutralia. I find it a great show and it has for one thing taught me that filleting a fish and cutting of its head is not scary to look at (even though I haven’t done it myself yet) and it showed me lots of different recipes.

So when I googled a chocolate mousse recipe and found one from the show I couldn’t do otherwise than try it. Actually, I found a website page presenting me with three different chocolate mousse recipes (one from every judge). Since making this chocolate mousse was a pretty spontaneous idea I simply selected that recipe I had all ingredients in my cupboard already: Matt’s recipe.

Chocolate mousse - stabilizing a foam
Author:
Cook time:
Total time:
Serves: 4 large bowls
Ingredients
  • 170g chocolate (I used extra dark, but feel free to use milk or regular dark, I like my mousse bitter and not that sweet)
  • 80 ml milk
  • 2 egg yolks
  • 4 egg whites
  • 2 tbsp granulated sugar (regular sugar, I prefer to use a fine version which has slightly smaller crystals)
Instructions
  1. Melt the chocolate au bain marie (in a bowl above a pot of boiling water), or in the microwave (the easy way, but be sure not to put it in too long in one go or it might burn).
  2. Mix in the milk in the chocolate. You will see little threads forming at first but when you continue mixing it should become one nice goey mass.
  3. Cool it down to just a little above room temperature and whisk in the egg yolks (it the mix is hot at this point you egg yolk might set or curdle, which you definitely don't want).
  4. Whisk the 4 egg whites with the sugar until you have really nice firm peaks (I greatly advise using a KitchenAid stand mixer here, it is sooo much easier to get a strong foam, if it's not as firm it will collapse easily in the next step).
  5. Carefully pour about a third of the egg whites into the bowl with the chocolate and gently fold it together (don't use a whisk here, instead use a spatula, else you'll break up all the air bubbles).
  6. Once all the egg whites are incorporated properly pour the mixture with the rest of the egg whites. Since you've already mixed part of the egg whites in it is a lot easier to mix in the rest.
  7. Place in the fridge straight away (or eat immediately) and leave there until you're planning to eat it (feel free to take it out a couple of minutes before eating to get to room temperature again).

This recipe worked out great for me and of course I’ve got an analysis for you on why it worked so well.

Melting the chocolate

Never melt chocolate in a pan on the fire directly. Reason is that with this direct way of heating the chocolate burns really very easily. For chocolate to melt well you need to make sure the fat melts, without the other parts of the chocolate burning before. That’s why people advise the au-bain-marie method (in a bowl above a pan with boiling water).

I personally only use that method when I already have a pan on the fire for something else (if a sauce is bubbling away, just put your chocolate bowl above!). In all other cases I use the microwave. The waves will heat up the chocolate fat and melt it. Take care that a microwave has hot spots and cold spots. This can result in part of your chocolate being very hot (and burning) whereas the rest is still solid. Therefore, always take out the chocolate every 30-6os to stir out around. That way you distribute the heat and make sure that another part sits in the hot spot.

A rich cool ganache

Whisking in a liquid in melted chocolate is always nice to see. You can actually see a transformation of the material. The chocolate will become uneven and you’ll see little threads when you add some liquid. If it’s only a little liquid all your chocolate can thicken up. However, if you add enough (as is the case here) you will liquefy the mix again, making a ganache. Ganaches are great by themselves for topping a cake for instance but are also a nice firm structure for our mousse.

We make the chocolate mousse even richer by whisking in some egg yolks. Egg yolks contain quite a bit of fat which will make your mousse even more creamy. Do take care to only mix in the egg whites once the chocolate ganache has cooled down a little (at least below 50°C). If it’s too hot the egg yolks will cook which won’t improve your ganache.

Yes, this mousse contains raw eggs if you don’t use pasteurized eggs. Decide whether this is a risk you are willing to take (not advisable for young children, pregnant women or other groups at risk for food poisoning).

Whisking the egg whites

Next step is whisking the egg whites. This is what will make your mousse nice and airy. A chocolate mousse has to contain air to be a mousse and this is the only step where that air is actually introduced.

As you might remember, egg whites consist of mostly water and proteins. When whisking the egg whites air is incorporated. If you would do this with normal water you would also see some foam. However within a second all the foam is gone again. That’s where these egg proteins come in. The egg proteins like to sit at the interface between water and air. This way they prevent the air bubbles from disappearing again.

Sugar in this egg white foam has two functions here. First of all, it gives the chocolate mousse some sweetness. At the same time though it helps increase and stabilize the egg foam volume. The sugar dissolves in the water, making the water a little more viscous, which makes it harder for the air bubbles to travel through. This allows the walls between the air bubbles to be thinner as well, resulting in more walls, thus more air bubbles thus a larger egg foam.

chocolate mousse

A chocolate mousse is a stable foam

Mixing the foam and the chocolate is always a careful thing. If you mix very vigorously you will break up the air bubbles and set them all free. If you don’t mix enough you wil still have some egg white foam in your chocolate mousse (yes, that is what those white spots in my mousse are, I actually thought it looked pretty fun).

Loose egg foam will make your chocolate mousse more unstable. This has to do with the way the mousse is stabilized. If you would leave your egg white on the kitchen counter you can see it decreasing in volume. If you’d come back an hour later or so it will have shrunk considerably. It will have to be stabilized. This is where the chocolate ganache comes in!

Chocolate fat has been melted at the start, but now we want it to set again. Preferably quick, which is why we put it in the fridge. The chocolate fat will set, become solid and will prevent the air bubbles from moving around.

Another reason for placing it in the fridge in this case is the fact that the eggs haven’t been cooked. So they might contain harmful micro organisms. These won’t grow when the mousse is placed in the fridge.

2 Comments

    • 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.
      Good luck!

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