Espresso Chocolate Mousse Layer Cake
The perfect layer cake begins with a moist chocolate cake, is filled with a rich espresso chocolate mousse whose scent will knock your socks off, and frosted with a delicious chocolate frosting.
For the Coffee Mousse
- 1 tablespoon + 1 teaspoon Unflavored gelatin I used Knox
- 2 tablespoons Espresso powder
- 1/4 cup Cold water
- 1/2 cup Boiling water
- 1 1/4 cup Granulated sugar
- 1/3 cup heaping Cocoa powder
- ½ cup very cold Coffee Liqueur (like Kahlua or Avion)
- ½ cup Cold brew concentrate or super dark espresso cold
- 3 cups Heavy cream very cold
- 1 tablespoon Vanilla extract
For the chocolate cake
- 1/2 cup Bittersweet chocolate chopped
- 3 tablespoons Unsweetened Dutch processed cocoa powder
- 1 cup Hot coffee
- 2 ¼ cups All-purpose flour spooned then leveled
- 2 teaspoons Baking powder
- 1 teaspoon Baking soda
- 1/2 teaspoon Salt
- 1 cup 2 sticks Unsalted butter, at room temperature
- 2 cups Granulated sugar
- 1/4 cup Firmly packed brown sugar
- 3 Large eggs at room temperature
- 2 1/2 teaspoons Vanilla extract
- 1 cup Whole milk
For the chocolate buttercream frosting
- 1/2 cup 1 stick Unsalted butter, at room temperature
- 3/4 cup Dutch processed cocoa powder
- Pinch table salt
- 4 cups Confectioners' powdered sugar
- 3/4 cup Heavy cream cold
- 2 1/2 teaspoons Vanilla extract
- Melted chocolate for drizzle
- Coffee Beans
Make the Coffee Chocolate Mousse:
Sprinkle gelatin in a small bowl. Add cold water and espresso powder. Stir briefly. Let stand until the gelatin has soaked up the water, about 1 minute or so.
Add boiling water to the bowl and stir until the gelatin is completely dissolved. Set aside to cool completely.
Combine the cold brew concentrate and the coffee liqueur in a measuring cup. Set aside briefly.
In a bowl of an electric stand mixer fitted with a whisk attachment (a hand mixer works wonderfully here too) combine the sugar and the cocoa powder. Add the heavy cream and mix over medium/high speed until the mixture thickens. In a slow stream pour the cold brew/coffee liqueur mixture, followed by the vanilla extract, and finally the gelatin mixture.
Increase the speed to high and continue whisking until thickened, about 1 minute or so. Remove bowl from mixer and test thickness by dipping the whisk into the mousse and lifting. If the mousse does not immediately dissolve onto itself it's ready. You want the mousse thick enough to form shapes that will not dissolve easily.
Spoon the mousse into a container with a tight-fitting lid and place in the freezer to chill for at least one hour.
Bake the cake:
Preheat the oven to 350 degrees Fahrenheit (180 degrees C) and place the oven rack in the center of the oven. Butter or spray with a nonstick vegetable spray, three - 8 x 2 inch deep round baking pans. Line the bottoms of the pans with parchment paper and set aside.
In a small heatproof bowl, place the finely chopped unsweetened chocolate and cocoa powder. Add the hot coffee and stir until the mixture is melted and smooth. Set aside to cool to room temperature. To a medium bowl, add the flour, baking powder, baking soda, and salt. Stir quickly with a fork to combine.
In the bowl of your electric mixer, fitted with a paddle attachment (a hand mixer works here as well) over medium/high speed, beat the butter and sugars until the mixture is light and fluffy, about 3-4 minutes. Add the eggs one at a time beating well after each addition. Stop the mixer and scrape the sides of the bowl. Turn the mixer to low/medium speed. Add the vanilla extract and melted chocolate mixture and beat to combine. The mixture should look sort of billowy, like a mousse.
Reduce the speed to low. Add the flour mixture alternating with the milk, beginning and ending with the flour mixture. Beat until the ingredients are incorporated, but be sure not to over mix or the cake will be tough.
Divide the batter evenly between the three prepared pans. Bang the pans on your counter to smooth out the batter and remove any air bubbles. Place in the oven and bake for about 25-30 minutes or until a toothpick inserted in the center comes out clean and the cake starts to separate from the sides.
Remove pans from oven and place on a wire rack to cool for about 8-10 minutes. Carefully invert the cakes (one at a time) over the wire rack and lift the pan. Remove the parchment paper and then, to prevent cracks, reinvert the cake onto a wire rack so that tops are right side up. Allow the cakes to cool completely. While the cakes bake, make the chocolate buttercream frosting.
Add height to your spring-form pan by lining it with a ring of parchment paper about 2-3 inches deep and set aside.
Make the chocolate buttercream frosting:
In a bowl of an electric mixer fitted with a whisk attachment, whip butter, cocoa powder, and salt over medium/high speed until combined. Turn the mixer off and add the confectioners' sugar all at once. Turn the mixer on to the lowest speed and whip until the confectioners' sugar is completely combined with the butter/cocoa powder mixture. Do not start the mixer at high speed or you will have confectioners' sugar in your face.
Once the mixture is combined, increase the speed to medium/high and continue whipping until combined, about 3-5 minutes. The mixture will looks a bit sandy and dry at this point. That’s fine. Stop and scrape the mixer to incorporate.
Turn the mixer to medium/high speed and add the heavy cream in 2 parts, allowing the heavy cream to thicken each time before adding in more cream. Add the vanilla extract and continue whipping the frosting until very light and fluffy, 3-5 more minutes.
Turn off mixer and remove bowl. Cover with plastic wrap and place in the refrigerator until ready to use.
Spoon about a cup of buttercream frosting into a piping bag fitted with a round tip. Set aside briefly.
Place your collared spring form pan on a flat surface. Begin by placing a layer of chocolate cake in the bottom of the spring form pan. With your piping bag, squeeze buttercream over the perimeter of the cake layer, leaving the center free of buttercream. Spread half the coffee mousse in the center, smoothing flat with an offset spatula. Place a layer of chocolate cake over the mousse. Repeat with second layer. Top with final layer of chocolate cake. Cover the cake with plastic wrap and place in the freezer to set completely, at least 2 hours, preferably 3.
Remove cake from freezer and chocolate buttercream from the fridge. Frost the cake with the chocolate buttercream, smoothing with an offset spatula as best you can.
Drizzle with melted chocolate and sprinkle coffee beans, if desired.
Serve and enjoy.