Decadent Chocolate Mousse Cake Recipe

This recipe creates a stunningly rich and decadent chocolate mousse cake that is sure to impress. It features two layers of moist, dark chocolate sponge cake, sandwiching a generous, thick layer of light and airy chocolate mousse. The entire cake is then enrobed in a glossy, mirror-like chocolate ganache glaze, which adds an extra layer of chocolatey richness and a beautiful, professional finish. This isn’t just a dessert; it’s a celebration of chocolate in three distinct and harmonious textures—a soft, tender cake, a silky-smooth mousse, and a firm, rich glaze. Perfect for special occasions, holidays, or any time you need an intensely chocolatey indulgence.

INGREDIENTS:

For the Chocolate Sponge Cake:

• 1 3/4 cups all-purpose flour
• 1 3/4 cups granulated sugar
• 3/4 cup unsweetened cocoa powder, high-quality
• 1 1/2 teaspoons baking soda
• 1 1/2 teaspoons baking powder
• 1 teaspoon salt
• 2 large eggs, at room temperature
• 1 cup buttermilk, at room temperature
• 1/2 cup vegetable oil
• 2 teaspoons vanilla extract
• 1 cup strong black coffee, hot

For the Chocolate Mousse:

• 1 1/2 cups heavy cream, divided
• 9 ounces high-quality dark chocolate (60-70% cacao), chopped
• 1/2 cup granulated sugar
• 2 teaspoons unflavored gelatin powder
• 1/4 cup cold water
• 2 large egg whites, at room temperature

For the Chocolate Ganache Glaze:

• 1 1/2 cups high-quality dark chocolate (60-70% cacao), finely chopped
• 1 1/4 cups heavy cream
• 2 tablespoons unsalted butter, softened

For Assembly and Garnish:

• A few fresh mint leaves or red berries (optional, for garnish)

INSTRUCTIONS:

Step 1: Prepare the Chocolate Sponge Cake

1. Preheat your oven to 350°F (175°C). Grease and flour an 8×8-inch square baking pan (or two 8-inch round pans) and line the bottom with parchment paper. This recipe makes a tall cake, so ensure your pan has high sides.
2. In a large bowl, whisk together the flour, sugar, cocoa powder, baking soda, baking powder, and salt. Sift the mixture to remove any lumps.
3. In a separate medium bowl, whisk together the eggs, buttermilk, vegetable oil, and vanilla extract until well combined.
4. Pour the wet ingredients into the dry ingredients and mix on low speed with a hand mixer (or with a whisk) until just combined. The batter will be thick.
5. Carefully pour the hot coffee into the batter, mixing on low speed until the batter is smooth and very liquidy. Do not overmix. The hot coffee “blooms” the cocoa powder, intensifying the chocolate flavor.
6. Pour the thin batter evenly into the prepared pan. Bake for 30-35 minutes, or until a wooden skewer inserted into the center comes out clean.
7. Let the cake cool in the pan on a wire rack for 15 minutes before carefully inverting it onto the rack to cool completely. Once cool, use a large, serrated knife to carefully slice the cake horizontally into two even layers.

Step 2: Make the Chocolate Mousse

1. Place the chopped dark chocolate in a heatproof bowl. In a small saucepan, heat 1/2 cup of the heavy cream over medium heat until it just begins to simmer. Pour the hot cream over the chopped chocolate and let it sit for 2-3 minutes. Whisk until the chocolate is completely melted and the mixture is smooth. Set aside to cool to room temperature.
2. In a separate small bowl, sprinkle the gelatin powder over the cold water. Let it sit for 5 minutes to bloom. Microwave the gelatin mixture for 10-15 seconds, or until it becomes a clear liquid. Stir and let it cool slightly.
3. Add the bloomed gelatin to the cooled chocolate mixture and whisk to combine.
4. In a clean bowl of a stand mixer fitted with the whisk attachment, or using a hand mixer, whip the remaining 1 cup of heavy cream on medium-high speed until it forms soft peaks. Do not over-whip.
5. In another very clean, separate bowl, beat the egg whites on medium speed until foamy. Slowly add the granulated sugar and beat on high speed until stiff, glossy peaks form.
6. Gently fold the cooled chocolate mixture into the whipped cream until no streaks of chocolate remain. Then, very carefully fold the whipped egg whites into the chocolate-whipped cream mixture in two additions. The key is to fold gently to maintain the airy texture of the mousse.

Step 3: Assemble the Cake

1. Place one layer of the cooled chocolate sponge cake back into the cleaned and lined baking pan. Or, for a neater result, place a cake ring or an 8×8-inch square frame around the cake layer.
2. Carefully pour the prepared chocolate mousse over the cake layer, using a spatula to spread it evenly to the edges.
3. Place the second cake layer on top of the mousse, pressing down very gently.
4. Cover the pan with plastic wrap and refrigerate for at least 4 hours, or preferably overnight, to allow the mousse to set completely.

Step 4: Create the Ganache Glaze and Finish the Cake

1. When the mousse is fully set, prepare the ganache glaze. In a heatproof bowl, combine the finely chopped dark chocolate and softened butter.
2. In a small saucepan, heat the heavy cream over medium heat until it just begins to simmer. Pour the hot cream over the chocolate and butter mixture. Let it sit for 2-3 minutes.
3. Whisk the mixture from the center outwards until it’s completely smooth and has a beautiful, glossy shine.
4. Remove the cake from the refrigerator and carefully un-mold it. Place the cake on a wire rack set over a baking sheet or tray to catch any drips.
5. Pour the warm ganache glaze over the top center of the cake, allowing it to naturally drip down the sides. Use an offset spatula to gently nudge the ganache over any bare spots on the top and sides, but do not spread it too much, as you want to maintain the smooth, mirror-like finish.
6. Allow the ganache to set at room temperature for about 30 minutes, or in the refrigerator for 10-15 minutes, until it is no longer sticky to the touch.
7. Transfer the cake to a serving platter. Garnish with fresh mint leaves or red berries, if desired. Serve chilled. This cake is a showstopper and best enjoyed when sliced with a hot knife for clean cuts.