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chocolate raspberry mousse cake with dripping chocolate ganache on a pink cake stand

Chocolate Raspberry Mousse Cake

Tara Kringlen
Rich chocolate cake layers form the base of this decadent chocolate raspberry mousse cake. Sandwiched between the moist cake layers is a tangy and sweet raspberry mousse. The cake is frosted in a lightly sweet but buttery raspberry swiss meringue frosting and then covered in a bittersweet chocolate ganache. Leftover ganache is whipped to form pretty swirls of chocolate on top of the cake between more raspberry buttercream.
5 from 3 votes
Prep Time 2 hrs
Cook Time 20 mins
Total Time 2 hrs 20 mins
Course Dessert
Cuisine American
Servings 12 slices
Calories 643 kcal

Ingredients
  

Chocolate Cake

  • 1 cup all-purpose flour
  • 1 cup granulated sugar
  • ½ cup natural cocoa powder unsweetened
  • ½ teaspoon baking powder
  • ½ teaspoon baking soda
  • ½ teaspoon kosher salt
  • ½ cup buttermilk
  • 2 eggs
  • cup vegetable oil
  • 1 teaspoon vanilla extract
  • ½ cup hot coffee

Raspberry Mousse

  • 6 oz fresh raspberries
  • cup sugar
  • 1 tablespoon lemon juice
  • 1 cup heavy whipping cream
  • 1 packet (1 ½ teaspoons) unflavored gelatin

Raspberry Swiss Meringue Buttercream

  • 4 egg whites
  • 1 ⅓ cups sugar
  • 1 cup unsalted butter cubed into tablespoons and at cool room temperature (60-65 degrees)
  • ¼ teaspoon salt
  • 1 teaspoon vanilla extract
  • 4 oz fresh raspberries

Chocolate Ganache

  • 4 oz bittersweet chocolate finely chopped
  • ½ cup heavy whipping cream

Instructions
 

Chocolate Cake

  • Preheat the oven to 350 degrees. Prepare 3, 6 inch cake pans with cooking/baking spray and line the bottoms with parchment paper (trace the bottom of the pan onto parchment paper and then cut out a circle).
  • In a medium bowl, combine flour, sugar, cocoa powder, baking powder, baking soda and salt.
  • In a small bowl combine the buttermilk, oil, eggs and vanilla.
  • Stir the wet ingredients into the dry ingredients until just combined. Pour in the hot coffee and stir until combined.
  • Divide the cake batter between the 3 pans evenly. Bake for 20-22 minutes until a cake tester inserted into the middle of the cakes comes out clean. Let the cakes cool in the pans for about 15 minutes and then turn out onto a wire rack to cool completely.

Raspberry Mousse

  • In a small bowl, sprinkle the gelatin over ¼ cup of water and set aside.
  • Combine the raspberries, sugar and 1 tablespoon of water in a small saucepan over medium heat. Stir until the sugar fully dissolves and the raspberries soften.
  • Puree the raspberry mixture in a blender or food processor and then press it through a fine mesh sieve to get rid of the seeds.
  • Stir in the lemon juice and then pour it back into the saucepan over medium heat. Add the gelatin and bring the mixture to almost a boil while stirring constantly until the gelatin is fully dissolved. Remove it from the heat and let it cool for about 10 minutes.
  • In a medium bowl, whip the heavy cream to almost stiff peaks. Gently fold in the raspberry puree until combined. Refrigerate the mousse until you are ready to fill the cake layers but not longer than 30 minutes so it doesn't fully set.

Raspberry Swiss Meringue Buttercream

  • Puree the raspberries in a blender or food processor until smooth. Push the puree through a fine mesh sieve to separate the seeds from the puree. Discard the seeds and set aside the puree.
  • In a medium bowl set over a saucepan of about 2 inches of gently boiling water that is not touching the bowl, add the egg whites and sugar.
  • Constantly whisk the sugar and egg whites for about 4-5 minutes until the sugar has dissolved completely or an instant read thermometer reads 160 degrees. Test to make sure the sugar is completely dissolved by carefully rubbing a small amount of the mixture between 2 fingers. If it feels grainy continue cooking until the sugar is fully dissolved.
  • Remove the bowl and place into a stand mixer or use a hand mixer and mix on medium high to high speed for 10-15 minutes until a thick and glossy meringue forms with stiff peaks.
  • The bowl and the meringue should be cool to the touch so if it is not, let it cool before adding the butter.
  • Switch to the paddle attachment if using a stand mixer and add the butter cubes, one to two tablespoons at a time, mixing well after each addition until all the butter is incorporated. *See notes or blog post for troubleshooting if your frosting is runny or curdled.
  • Add the salt and vanilla and mix until combined.
  • Add the raspberry puree and beat until combined and smooth. If the frosting curdles or separates at this point, place the bowl back over the double boiler with simmering water for about 2 minutes to melt the sides of the buttercream. Place it back into the stand mixer and beat for another couple minutes until it comes together and is light and fluffy.

Chocolate Ganache

  • Wait to make the ganache until you are ready to decorate the cake. Place the chopped chocolate in a small bowl and set aside.
  • Heat the heavy cream in the microwave for 30-45 seconds until slightly bubbling at the edges.
  • Pour the hot cream over the chocolate and place a plate or plastic wrap over the bowl. Let it sit for about 2-3 minutes.
  • Stir the cream and chocolate until it is fully melted and completely combined. Let it cool for 5 minutes but no longer as it will become too thick to pour.

Assembly

  • Level each cake layer by using a serrated knife to make each one completely smooth on the top.
  • Place the first cake layer onto a cake stand or cake board using a small amount of frosting under the cake layer to keep it from sliding on the board.
  • Place half of the mousse over the first layer and spread it evenly over the cake and all the way to the sides.
  • Repeat with the next cake layer and the rest of the mousse and top it with the third cake layer.
  • Cover the cake with plastic wrap lightly and refrigerate the cake for at least an hour to let the mousse set up before frosting it.
  • Once chilled, do a crumb coat of the raspberry buttercream, lightly frosting the top and sides of the cake. Chill for at least 15 minutes.
  • After the cake has chilled for 15 minutes, frost the cake with the rest of the buttercream, smoothing the tops and sides as you prefer.
  • Use a spoon to pour a little bit of the slightly cooled ganache on the edge of the cake, letting it drip down the sides. Use the spoon to help it drip if needed. Repeat this for as many drips as you would like around the cake. If your drip is running too quickly down the cake and pooling at the bottom then let it cool a little longer before doing the rest of the drips. Fill in the top of the cake with more ganache, being careful to not let any more drip down the edges.
  • Decorate the cake with more frosting as desired. I piped swirls of frosting onto the top of the cake using a 1M open star tip and then whipped the remaining chocolate ganache with a hand mixer and piped those alternately with the buttercream.

Notes

  • See the post for important troubleshooting tips for the swiss meringue buttercream.
  • Store any leftovers covered in the refrigerator for up to 5 days.

Nutrition

Serving: 1sliceCalories: 643kcal
Keyword chocolate cake, raspberry mousse
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