Chocolate Mousse Cake Recipe - Soft & Moist (2024)

5 from 51 votes

Prep 1 hour hour 15 minutes minutes

Cook 18 minutes minutes

Chill Time 12 hours hours

Total 13 hours hours 33 minutes minutes

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Chocolate mousse

• ▢ 3 cups heavy whipping cream, divided
• ▢ 8 large egg yolks
• ▢ ¼ cup granulated white sugar
• ▢ 18.5 oz high-quality semi-sweet chocolate bars, melted Use only high-quality chocolate bars for the mousse instead of chocolate chips.
• ▢ ¾ cup powdered sugar, sifted

Chocolate cake layer

• ▢ 1 cup all-purpose flour, spooned and leveled
• ▢ ⅜ cup dutch-processed cocoa powder, spooned and leveled
• ▢ ¾ cup granulated white sugar
• ▢ 1 ½ teaspoon baking powder
• ▢ ½ teaspoon salt
• ▢ ¼ cup mild vegetable or canola oil
• ▢ 1 large egg
• ▢ ¼ cup buttermilk
• ▢ 1 teaspoon vanilla extract
• ▢ ¼ cup hot cocoa (unsweetened beverage)

Chocolate glaze

• ▢ 6 oz high-quality semi-sweet chocolate, finely chopped
• ▢ ¾ cup heavy whipping cream

• Make the chocolate mousse: In a medium saucepan, whisk together 1 ½ cups heavy cream, egg yolks, and sugar and cook over medium-high heat, until it thickens and coats the back of a spoon, about 1-2 minutes. Whisk continuously. Remove from the heat and continue whisking for about 1-2 minutes. Add melted chocolate and whisk until combined. Transfer the chocolate custard to a large mixing bowl and let cool completely.

• Preheat the oven to 350°F/175°C. Line the bottom and the sides of a 9" / 23cm baking pan with parchment paper and set aside.

• Make the chocolate cake layer: In a medium-sized bowl, mix together the flour, cocoa, sugar, baking powder, and salt and set aside. In a large mixing bowl, using an electric mixer fitted with a whisk or paddle attachment, beat the oil, egg, buttermilk and vanilla, just until combined. Stir in dry ingredients to combine. Slowly mix in the hot cocoa until well combined. The batter will be thin. Pour the batter into the prepared baking pan and bake 14-18 minutes or until a toothpick inserted into the center comes out clean. Leave to cool in the pan for about 20 minutes. Then open the springform pan and let it cool down to room temperature.

• Continue with the chocolate mousse: In a large mixing bowl, using an electric mixer fitted with a whisk attachment, beat the remaining 1 ½ cups heavy whipping cream until soft peaks form. Add powdered sugar and beat until stiff peaks form.

• Using a whisk, stir about ¼ of the whipped cream into the cooled chocolate cream until smooth and combined. Then carefully fold the remaining whipped cream into the chocolate mixture with a spatula until combined. Don't overwork the mousse or it won't set properly.

• Assemble the cake: Slice a thin layer from the top of the cooled cake layer to create a flat surface if needed. Attach the springform ring and close the pan. Then carefully pour the chocolate mousse into the pan and spread evenly. Chill in an airtight container in the refrigerator overnight.

• Make the chocolate ganache:Place chopped chocolate in a large heatproof bowl and set aside. Place heavy cream in another heatproof bowl and microwave until very hot, almost boiling, about 1-2 minutes. Pour over the chocolate and let stand 1-2 minutes. Whisk until smooth and the chocolate has completely melted. Chill in the fridge for about 10-15 minutes to thicken. Test the consistency of the ganache on the side of the bowl. It should drip. The longer it cools, the thicker it gets. If it's too firm, reheat it in the microwave for a few seconds. Once it has reached the desired consistency, it can be spooned onto the cake.

• Remove the ring from the springform pan and gradually spoon the ganache around the edges of the cake, letting it drip down the sides. Do this with a small spoon, making a drop at a time. Then spoon or pour the rest of the frosting onto the cake (you may not need all of it) and smooth with an offset spatula. Place the cake in the fridge for 15 minutes to allow the ganache to set. Decorate as you like. Store in an airtight container in the refrigerator for up to 3 days.

• Measure Dry Ingredients Properly. This is key for the best outcome of your chocolate cake layer. If you're not using a kitchen scale, fluff the dry ingredient up, then scoop it into the measuring cup with a spoon, and then level it with the back of a knife without packing. If you don't measure the dry ingredients correctly, the cake layer can become dry and hard.
• Do Not Over-Bake. The cake layer is very thin and over-bakes quickly.
• Cool Completely. Allow the cake base to cool completely before filling it with the chocolate mousse so the mousse will set properly.
• Chill Before Serving. Make sure you chill the cake in the fridge for at least 4 hours before serving as it needs time to set and chill properly. Do not put it in the freezer to speed up the cooling process.

Be sure to check the post above for more details about the ingredients, substitutions, and more tips for making this triple chocolate mousse cake.