The BEST Chocolate Mousse Cake Filling

This decadent chocolate mousse cake filling is rich, creamy, yet light and airy made with real chocolate, eggs, and whipped cream. Use it in between cake layers, fill it in a shortcrust pastry tart, or pour in a mold to make a chocolate mousse cake.

A chocolate mousse is a treat in any form, right? Whether it's served in a fancy dessert cup with a dollop of whipped cream or whether you have it in between two cake layers, you cannot forget that light and airy texture for anything else.

My mom would say a good mousse does not need an introduction. And, you should know what it is, the moment it hits your palette. It's the effort of adding all that whipped air into the ingredients making sure it's as light as can be.

Chocolate mousse is my favorite. And, as you can see, I have shared quite a few variations with you. For example, my classic mousse, vegan, eggless mousse as well as desserts like chocolate mousse cake with mirror glaze and chocolate mousse for two and cream cheese chocolate mousse tart.

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Ingredients and substitutes (pin)

• Milk - always use full-fat milk when making desserts so you don't have an issue with the milk solids and water separating when cooking
• Cream - I always use heavy whipping cream no less than 38% when making desserts
• Eggs - I use large eggs about 50 to 60 grams each. If you do have very small eggs you can add an extra egg yolk
• Chocolate - this is the star of this cake filling so you want to make sure you use good quality chocolate that you like to eat. Most of my desserts use between 65 to 70 % Callebaut chocolate.
• Egg whites - Adding whipped egg whites adds another layer of lightness to the mousse but you can omit the egg whites as well.
• Cream of tartar - this helps keep the protein and water in the egg whites from separating. You can also add the same amount of salt, lemon juice or vinegar instead.

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Step by step instructions

Double boiler

• Place a saucepan with 2-inches of water on medium heat. You will need 3 heat-proof bowls that can be set on the saucepan.
• Bowl 1 - In the first bowl, add the chocolate and butter. Place it over the saucepan with simmering water. Let the chocolate melt. Stirring when needed. Set aside to cool slightly.
  Pro tip - Chocolate can seize if any steam gets into it. So, keep the heat on medium to low and stir as necessary.
• Bowl 2 - In the second bowl, add the egg yolks and 2 tablespoon of sugar. Combine well. Then, place it over the saucepan with simmering water. Using a whisk, stir continuously until all the sugar is melted and the yolks are barely warm. And set aside.
  Pro tip - You want the heat to be on medium to low (not high) to prevent the eggs from cooking. You don't need a thermometer but as a guide, it should be about 149 F.
• Bowl 3 - In the third bowl, add the egg whites, salt, and the remaining 2 tablespoon of sugar. Place it over the saucepan with simmering water. Use a clean whisk to stir until all the sugar has melted. We want the mixture barely warm.
  Pro tip - Keep the heat on medium to low (not heigh) to prevent the eggs from cooking. You don't need a thermometer but as a guide, it should be about 144 F.

Whipping time

• In the bowl of a stand mixer with the whisk attachment, whip the whipping cream with vanilla extract to almost stiff peaks - And set aside.
• Using the same mixer and whisk attachment (no need to clean the bowl), whip the egg yolks until light and fluffy - set aside.
• Clean the mixer bowl and whisk attachment as we need a clean grease-free bowl. Then whip the egg whites to stiff peaks - And set aside.
  Pro tip - It is very important to clean the bowl and whisk as any grease will prevent the egg whites from whipping to a stiff meringue.

Assemble

• First, add the whipped yolks to the chocolate mixture - fold gently but don't overmix.
• Next, add the whipped cream to the chocolate mixture - fold gently but don't overmix.
• Finally, add the whipped egg whites to the chocolate mixture - fold gently until you have no white streaks.
• Your chocolate mousse is ready to be used between your cake layers. This will stay in the fridge for 3 to 4 days.

The right way to fill a cake?

If you are a cake decorator then by now you know what I mean when I say you need to have a buttercream or frosting dam around the edge of your cake layer before you add any soft filling be it this vanilla custard cake filling, strawberry, blueberry or any of those exotic cake filling recipes I have on this blog.

The frosting dam has to have a thick consistency in order to keep the filling from oozing out of the cake. Once you have a dam securing the filling you can do all kinds of decorations. Whether you just make a simple dessert cake or whether you want to cover it with fondant and add more accessories. See my video tutorial on how to level, torte, fill and frost a cake like a pro

Tips chocolate mousse

• Use good quality chocolate. No baking or cooking chocolate when making a mousse. 
• Chocolate can burn easily so make sure to keep the heat on low when melting. 
• Also, chocolate will seize with any steam or water droplets from the double boiler. So make sure to keep the heat low and work carefully 
• Eggs separate well when chilled because the yolks stay whole but eggs whip beautifully when warm. So separate cold eggs but whip when they are warm. 
• Again, when cooking the egg yolks and egg whites with sugar, don't make haste. While the sugar will help stabilize it can still curdle with high heat. So, keep the heat low and stir constantly. 
• When whipping egg whites make sure you clean the whisk attachment and bowl well. Otherwise, any grease on the bowl or whisk will prevent the eggs from whipping. 
• There are endless ways to flavor a chocolate mousse. The most common would be Baileys (use my homemade baileys) or Kahlua for me. In addition, you can also add berries such as raspberry, strawberry, or blueberry. Also, orange liquor, mint, or even licorice.
  And yet, a word of advice - make sure you are confident that your guest is going to appreciate the flavor you add. For example, I'm not a huge fan of the combination of orange or mint, with chocolate. So, never assume that everyone will like what you like.
• This mousse is delicious on its own and can be poured into glasses to make a dessert, molded into a cake pan to make a mousse cake, or filled in cake layers. 

What cake works best with chocolate mousse filling?

This is one of the most important questions you must be asking before you even start making your chocolate mousse cake filling? A mousse is a light and airy mixture so you want to avoid using dense cakes like chocolate mud cake. While the frosting dam will hold the filling what happens is the weight of the cake usually gets its way as soon as you cut into it. Everything just oozes out with the weight of the top layers.

So, what cake works best for light and airy cake fillings like this mousse or pastry cream? Here are some of my cake recipes that would work wonderfully.

• Simple Moist Chocolate Cake with American Buttercream
• Espresso Cake with Whipped Espresso Ganache
• Brown Butter Cake with Whipped Cream Buttercream
• Vanilla Cafe Latte Cake with Coffee Buttercream
• Classic Gingerbread Cake with Vanilla Buttercream and Ganache
• One Bowl Vanilla Cake - Naked Cake
• One Bowl Chocolate Cake - Naked Cake
• Earl Grey Cake with Italian Meringue Buttercream
• Chocolate Cake with Whipped Cream
• Light and fluffy Vanilla Cake
• Vanilla Cream Cake Recipe made with Fresh Cream
• Chocolate Chiffon Cake with Kahlua Chocolate Buttercream
• Devil's Food Chocolate Cake with Chocolate Ganache
• Gluten-Free Chocolate Cake

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Frequently asked questions

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