How To Make Delicious Dark Chocolate Mousse Cake From Scratch!

This delicious dark chocolate mousse cake blends unsweetened natural cocoa powder and dark cocoa powder to give you an extra rich taste making it the ideal dessert for any occasion.

This dark chocolate mousse cake is done in 3 parts:

  1. Dark chocolate cake
  2. Chocolate mousse
  3. Chocolate ganache


For dark chocolate cake

All-purpose flour – 1 ¾ cup
Unsweetened Cocoa powder – ¾ cup
Sugar granulated – 1 ¾ cup
Baking soda – 2 tsps
Baking powder – 1 tsp
Salt – 1 tsp
Espresso powder – 2 tsps (optional)
Vegetable oil – ½ cup
Eggs – large – 2
Sour cream – full fat – ¾ cup (room temperature)
Buttermilk – ½ cup
Vanilla extract – 2 tsps
Hot water or coffee – ½ cup
Mini or regular semi-sweet chocolate chips – 1 cup
Fresh berries and/or chocolate shavings – for decorating

For chocolate mousse

Hot water – ½ cup
Cocoa powder – ¼ cup
Semi-sweet chocolate bars – finely chopped – 2 (4-ounce quality)
Heavy or whipping cream – 2 cups
Icing sugar – 2 tbsps
Vanilla extract – ½ tsp

For chocolate ganache

Semi-sweet chocolate bars – finely chopped – 2 (4-ounce quality)
Heavy or whipping cream – 1 cup


• Preheat the oven to 350 degrees Fahrenheit (177 degrees Celsius). Grease four 8-inch or 9-inch cake pans, then line with parchment paper and grease that as well. The cakes are easier to remove from the pans when they are wrapped in parchment paper.

• To bake the cake: In a large mixing bowl, combine the flour, cocoa powder, sugar, baking soda, baking powder, salt, and espresso powder (if using) and set aside. On medium-high speed, whisk together the oil, eggs, and sour cream using a handheld or stand mixer fitted with a whisk attachment (or a whisk). Mix in the buttermilk and vanilla extract until everything is well mixed. Mix in the buttermilk and vanilla extract until everything is well mixed. Pour the wet ingredients into the dry ingredients, whisk or beat on low speed until the batter is thoroughly blended, then add the hot water/coffee and add in the chocolate chips, if needed.

• Divide the batter evenly among the four pans. Preheat the oven to 19-23 degrees Fahrenheit and bake for 19-23 minutes. Due to the variation in baking timing, it is important to be vigilant with your cakes.  When a toothpick inserted in the center comes out clean, that means the cakes are ready.

• Take the cakes out of the oven and place them on a wire rack to cool. Allow the pan to cool completely.

To make the chocolate mousse

• Prepare the chocolate mousse while the cakes cool so it may chill and be ready at the same time as the cake layers. You may make the mousse up to two days ahead of time. Combine the boiling water and cocoa powder in a mixing bowl. Remove from the equation. In a double boiler or in the microwave, melt the chopped chocolate bars. Place the chopped chocolate in a medium heat-proof bowl if using the microwave. Microwave for 20 seconds at a time, stirring after each addition, until totally melted and smooth. Stir the boiling water/cocoa combination into the melting chocolate until it becomes thick and smooth and set it aside. Whip the heavy cream, icing sugar, and vanilla extract on medium-high speed with a hand mixer or a stand mixer fitted with a whisk attachment for about 3-4 minutes. Once the mixture turns loose, pour in the chocolate mixture and stir gently using a spoon or rubber spatula. Overmixing might cause the mousse to collapse or thin out. Refrigerate the mousse and keep it covered for a minimum of 2 hours and maximum up to 2 days. This makes approximately 4.5 cups chocolate mousse.

• Prepare the layers before making the chocolate ganache: To begin, level the cakes, if necessary, by slicing a small layer off the tops of the cakes using a broad serrated knife to achieve a flat surface. 1 cake layer should be placed on a cake stand or serving dish. Cover the top of the cake with roughly 1.5 cups chocolate mousse using a big icing spatula. Place the second layer on top and spread 1.5 cups chocolate mousse equally across the top. Spread another 1.5 cups mousse evenly on top of the third cake layer. Save a spoonful of mousse for a thin crumb coating. Finish with the fourth and final cake layer. For the crumb coat, spread the remaining mousse around the sides. Scrape the crumb coat off the cake using a bench scraper. Refrigerate for at least 1 to 4 hours before serving. While you're waiting, make the ganache.

To make the chocolate ganache

• Chop the chocolate and place it in a medium heat-resistant dish. In a small saucepan, boil the cream over medium heat until it begins to softly simmer. (Do not bring to a fast boil– it will be too hot!) Pour over the chocolate, then set it aside for 2-3 minutes to allow the chocolate to melt. Slowly whisk with a metal spoon or a tiny rubber spatula until the chocolate has melted and the mixture is smooth. The finer the chocolate is cut, the faster it melts with the cream. Do not microwave it if it is not melting. Allow the ganache to cool for 20 minutes at room temperature before spreading on the chilled cake.

• Spread ganache over the cooled cake. Use an icing spatula to smooth the top and a bench scraper to smooth the sides. Garnish with fresh berries and/or chocolate shavings, if necessary. Serve immediately or refrigerate for up to 4-6 hours before serving, uncovered. The cake can be served cold or at room temperature.

• Refrigerate leftover cake securely covered for up to 5 days.

Recipe Source: Sally's Baking Addition