How to Make a Stunning Chocolate Mousse Cake

A towering cake filled with mousse? Sign us up! Learn how to make a four-layer chocolate mousse cake to get your cocoa fix.

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Craving an exceptionally decadent dessert? Then it has to be mousse! There are so many delicious ways to enjoy mousse, but sandwiched between layers of decadent chocolate cake has to be one of the best.

How to Make 4-Layer Chocolate Mousse Cake

This towering chocolate mousse cake comes to us from Kathy Kittell in Lenexa Texas. She says, “Here’s to that chocolate fix we all need!”

Ingredients

For the cake:

  • 3/4 cup butter, softened
  • 1-1/2 cups sugar
  • 1 large egg
  • 1 teaspoon vanilla extract
  • 1 cup buttermilk
  • 3/4 cup sour cream
  • 2 cups all-purpose flour
  • 2/3 cup baking cocoa
  • 1 teaspoon baking soda
  • 1/4 teaspoon salt

For the chocolate mousse filling:

  • 8 ounces semisweet chocolate, chopped
  • 2 cups heavy whipping cream
  • 1 teaspoon vanilla extract

For the ganache:

  • 16 ounces semisweet chocolate, chopped
  • 1/2 cup butter, cubed
  • 1-1/2 cups heavy whipping cream

Tools You’ll Need

  • Stand mixer: This cake requires a lot of mixing, not just for the mousse, but for the cake batter and ganache. A stand mixer is always a big help.
  • 8-inch cake pans: You’ll need two 8-inch cake pans for this recipe. Make sure you have them on hand to make this layered masterpiece.
  • Serrated bread knife: Those two cake layers will be doubled. A serrated knife makes slicing the rounds in half easy.

Directions

Step 1: Make the cake batter

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This chocolate mousse cake starts with butter and sugar. Cream them together in the bowl of a stand mixer for 5 to 7 minutes—until light and fluffy. Then beat in the egg and vanilla extract.

While those ingredients are whizzing away in the mixer, stir the sour cream and buttermilk together in a small dish. These ingredients will help make an extra tender cake. In another bowl, whisk together the flour, cocoa powder, baking soda and salt.

Then alternate adding the dry ingredients and the buttermilk-sour cream to your mixing bowl. Be sure to beat well after each addition.

Step 2: Bake the cakes

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Next, grease and line two 8-inch cake round cake pans. Divide the batter evenly between both pans. Then bake at 350ºF for 30 to 35 minutes or until a toothpick inserted in the center comes away with a few crumbs.

Remove the cakes from the oven and let them cool for 10 minutes. Then turn the cakes out onto wire racks to cool completely.

Step 3: Make the mousse filling

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As the cakes are baking and cooling, you can start making the star of the show: the chocolate mousse! Start the mousse by melting the chocolate and cream together on low heat. Don’t rush this process or be tempted to crank up the heat. Low and slow is the best way to melt chocolate over the stove.

Once fully melted, remove from the heat and stir in the vanilla extract. Transfer the mixture to a bowl and chill until slightly thickened. Pop into the fridge on occasion to give it a stir. This will help you keep an eye on the chocolate as it thickens.

Once cooled and thickened, beat the chocolate on medium speed until it gets light and fluffy. Return the mousse to the fridge until it achieves spreading consistency.

Step 4: Make the ganache

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Besides being full of lush chocolate mousse, this cake is topped with decadent ganache. To make the ganache icing, start by heating chocolate and butter together in a saucepan until melted. Again, do this on low heat and take your time. Once melted, slowly add the cream and heat until warmed.

Transfer the ganache to a bowl and chill until it’s spreadable like frosting.

Step 5: Layer and frost

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To transform the two cake layers into four, grab your go-to serrated bread knife. Very carefully slice the layers in half with a gentle sawing motion, much like you’d tort a cake.

Place the first layer of cake onto your favorite cake stand or cake plate. Then evenly spread a third of the chocolate mousse over the top. Repeat with the remaining layers of cake and mousse.

All that’s left is to frost the outside of the cake with the creamy chocolate ganache. The spreadable ganache will work similarly to your go-to buttercream frosting. Use an offset spatula and take your time making a smooth and appealing finish. Looking for more? Learn how to make chocolate mousse pie.

Editor’s Tip: If your mousse or ganache has firmed up too much in the fridge, let it sit at room temperature until it reaches a spreadable consistency. Don’t microwave! Let time and room temperature do their work.

Tips for Making Chocolate Mousse Cake

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Can you make chocolate mousse cake ahead of time?

You can make chocolate mousse cake in advance. For the best texture and flavor, only make the cake a day in advance.

Be sure to store the cake in the refrigerator. Take the cake out of the fridge and let it sit at room temperature for about 45 minutes before slicing and serving. This allows the mousse and ganache to get back to their creamy, rich textures.

How can you make chocolate mousse cake your own?

There are so many fun ways to customize a chocolate mousse cakes to suit your tastes—both for flavor and aesthetics:

  • Pump up the flavor: This chocolate mousse cake is flavored with chocolate and vanilla extract. This is a classic combo, but you can layer on even more flavors. Try adding a bit of orange liqueur like in this Julia Child mousse recipe. You can also add a touch of mint extract (use this sparingly!). If you want to add some crunch, sprinkle toasted nuts between the layers or over the top of the cake.
  • Add decorations: Our Test Kitchen kept the decoration on this cake simple, but that doesn’t mean you have to! Use buttercream and try your hand at piping a message or flowers on top. Also, sprinkles are always welcome on top of a cake.
  • Try it naked: You read that right! But we mean naked in the cake sense. Naked cakes allow you to get a peek at all the decadent filling inside a cake. What better way to show off the lush chocolate mousse inside this layer cake?

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Lisa Kaminski
Lisa is a former Taste of Home editor and passionate baker. During her tenure, she poured her love of all things sweet (and sometimes savory) into Bakeable, Taste of Home's baking club. Lisa also dedicated her career here to finding and testing the best ingredients, kitchen gear and home products for our Test Kitchen-Preferred program. At home, you'll find her working on embroidery and other crafts.