Chocolate Mousse Cake

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)

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