This Chocolate Mousse Cake is a decadent treat that combines a rich chocolate cake with creamy chocolate mousse and a glossy ganache glaze. Perfect for special occasions or when you want to indulge in a chocolate lover’s dream!
Ingredients
For the Chocolate Cake:
3/4 cup (94 g) unbleached all-purpose flour
3 tablespoons (15 g) unsweetened Dutch-processed cocoa powder
1/2 teaspoon baking powder
1/4 teaspoon baking soda
1/4 teaspoon salt
1/2 cup (100 g) granulated sugar
1 large egg, room temperature
3 ounces (85 g) plain whole milk yogurt, room temperature
1/4 cup (60 ml) coffee, room temperature
3 tablespoons (45 ml) flavorless oil (e.g., vegetable oil)
1/2 teaspoon vanilla extract
For the Chocolate Mousse:
8 ounces (226 g) semi-sweet chocolate bars, finely chopped
2 1/4 cups (540 ml) heavy whipping cream, cold, divided
4 large egg yolks
1/4 cup (50 g) granulated sugar
1 teaspoon (3 g) unflavored gelatin powder
2 tablespoons (30 ml) cold water
1 teaspoon vanilla extract
For the Chocolate Ganache Glaze:
8 ounces (226 g) semi-sweet chocolate, finely chopped
1 cup (240 ml) heavy whipping cream
1 tablespoon (14 g) unsalted butter, softened (optional)
For the Whipped Chocolate Buttercream:
1 cup (226 g) unsalted butter, room temperature, slightly firm to touch
2 cups (220 g) confectioners’ (powdered) sugar, sifted
1/4 cup (20 g) unsweetened Dutch-processed cocoa powder
2-3 tablespoons (30-45 ml) heavy whipping cream, room temperature
1/2 teaspoon salt
1 teaspoon vanilla extract (optional)
For Assembly:
Chocolate pearls (optional)
Instructions
Prepare the Chocolate Cake:
Preheat Oven: Preheat oven to 350°F (175°C). Grease and line the base of an 8 or 9-inch springform pan with parchment paper.
Mix Dry Ingredients: In a medium bowl, whisk together flour, cocoa powder, baking powder, baking soda, and salt.
Cream Wet Ingredients: In a stand mixer bowl (or using a hand mixer), beat oil and sugar together until fluffy, about 1-2 minutes. Mix in yogurt, then beat in the egg until fully incorporated.
Combine Ingredients: Reduce mixer speed to low. Alternately add the dry ingredients and coffee, starting and ending with dry ingredients. Mix until just combined.
Bake Cake: Spoon batter into prepared pan. Bake for 24-26 minutes or until a toothpick inserted into the center comes out clean. Cool in the pan for 45-60 minutes. Level the cake with a serrated knife and return it to the springform pan.
Prepare the Chocolate Mousse:
Dissolve Gelatin: In a small bowl, add cold water and sprinkle gelatin over it. Let sit for 5 minutes.
Make Custard: Whisk egg yolks and sugar until thickened. Heat 1 cup heavy cream in a saucepan until steaming but not boiling. Whisk the hot cream into the egg mixture slowly. Return the mixture to the saucepan and cook over medium-low heat, stirring constantly until it thickens and coats the back of a spoon, about 4-5 minutes (temperature should be 167-170°F / 75-77°C). Strain custard through a sieve into a bowl. Whisk in dissolved gelatin, chopped chocolate, and vanilla extract. Cool to room temperature, whisking occasionally.
Whip Cream: Whip remaining heavy cream to soft peaks. Fold half of the whipped cream into the cooled chocolate mixture, then fold in the remaining whipped cream.
Assemble Mousse Layer: Spoon mousse over the cooled, leveled chocolate cake. Smooth with a spatula. Refrigerate for 4-6 hours or overnight to set.
Prepare the Chocolate Ganache Glaze:
Make Ganache: Place chopped chocolate in a bowl. Heat heavy cream until steaming and pour over chocolate. Let sit for 1 minute, then whisk until smooth. Whisk in softened butter if using.
Glaze Cake: Chill the mousse cake in the freezer for 30 minutes. Place the cake on a parchment-lined baking sheet. Pour the ganache over the cake, spreading with an offset spatula if needed. Let set for 10-15 minutes in the fridge.
Prepare the Whipped Chocolate Buttercream:
Cream Butter: Beat butter until fluffy. Gradually mix in powdered sugar and cocoa powder until well combined. Add vanilla extract and heavy cream, adjusting the consistency as needed.
Frost Cake: Pipe medium-sized dollops of buttercream on top of the glazed mousse cake. Decorate with chocolate pearls if desired.
Enjoy this decadent Chocolate Mousse Cake with layers of rich chocolate flavor and smooth mousse! 
Prep Time: 45 minutes | Bake Time: 24-26 minutes | Chill Time: 4-6 hours | Total Time: Approximately 6 hours | Servings: 12 slices