Dark Chocolate Mousse Cake
Total Time
5 hours, 55 minutes (includes cooling)
Prep Time
2 hours, 30 minutes (includes chilling)
Cook Time
25 minutes
Rating
4.9 out of 5 stars
(350)
Ingredients
serves 12
- 1 and 3/4 cups (219g) all-purpose flour (spooned & leveled)
- 3/4 cup (62g) unsweetened natural cocoa powder
- 1 and 3/4 cups (350g) granulated sugar
- 2 teaspoons baking soda
- 1 teaspoon baking powder
- 1 teaspoon salt
- 2 teaspoons espresso powder (optional)
- 1/2 cup (120ml) canola or vegetable oil
- 2 large eggs, at room temperature
- 3/4 cup (180g) full fat sour cream, at room temperature
- 1/2 cup (120ml) buttermilk, at room temperature
- 2 teaspoons pure vanilla extract
- 1/2 cup (120ml) hot water or coffee
- optional: 1 cup (180g) mini or regular semi-sweet chocolate chips
- optional garnish: fresh berries and/or chocolate shavings
- Chocolate Mousse
- 1/2 cup (120ml) hot water
- 1/4 cup (22g) unsweetened cocoa powder
- two 4-ounce quality semi-sweet chocolate bars (113g each), finely chopped
- 2 cups (480ml) heavy cream or heavy whipping cream
- 2 Tablespoons (15g) confectioners’ sugar
- 1/2 teaspoon pure vanilla extract
- Chocolate Ganache
- two 4-ounce quality semi-sweet chocolate bars (113g each), finely chopped
- 1 cup (240ml) heavy cream or heavy whipping cream
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Preparation
Step 1
Preheat oven to 350°F (177°C). Grease four 8-inch or 9-inch cake pans, line with parchment paper rounds, then grease the parchment paper.
Step 2
Whisk the flour, cocoa powder, sugar, baking soda, baking powder, salt, and espresso powder (if using) together in a large bowl. Set aside.
Step 3
Using a handheld or stand mixer fitted with a whisk attachment, mix the oil, eggs, and sour cream together on medium-high speed until combined. Add the buttermilk and vanilla and mix until combined.
Step 4
Pour the wet ingredients into the dry ingredients, add the hot water/coffee, and whisk or beat on low speed until the batter is completely combined. Fold in the chocolate chips, if using.
Step 5
Divide batter evenly between 4 pans. Bake for 19-23 minutes. The cakes are done when a toothpick inserted in the center comes out clean.
Step 6
Remove the cakes from the oven and set on a wire rack. Allow to cool completely in the pan.
Step 7
As the cakes cool, prepare the chocolate mousse so it can chill and be ready at the same time as the cake layers. Whisk the hot water and cocoa powder together. Set aside.
Step 8
Melt the chopped chocolate bars in a double boiler or use the microwave. Pour hot water/cocoa mixture into melted chocolate and stir until thick and smooth.
Step 9
Using a hand mixer or a stand mixer fitted with a whisk attachment, whip the heavy cream, confectioners’ sugar, and vanilla extract together on medium-high speed until medium peaks form.
Step 10
Pour in the chocolate mixture and using a spoon or rubber spatula, gently fold together. Cover mousse and chill in the refrigerator for at least 2 hours.
Step 11
Level the cakes if needed. Place 1 cake layer on your cake stand or serving plate. Using a large icing spatula, evenly cover the top with about 1.5 cups chocolate mousse.
Step 12
Top with 2nd layer and evenly cover the top with 1.5 cups chocolate mousse. Top with the third cake layer, then spread another 1.5 cups mousse evenly on top.
Step 13
Top with final 4th cake layer. Spread any remaining mousse around the sides as a crumb coat. Refrigerate cake for at least 1 hour and up to 4 hours.
Step 14
Place chopped chocolate in a medium heat-proof bowl. Heat the cream in a small saucepan over medium heat until it begins to gently simmer.
Step 15
Pour over chocolate, then let it sit for 2-3 minutes to gently soften the chocolate. Stir until chocolate has melted and mixture is smooth.
Step 16
Let ganache cool for 20 minutes at room temperature before spreading on chilled cake.
Step 17
Pour/spoon ganache on chilled cake. Smooth the top with an icing spatula and the sides with a bench scraper.
Step 18
Top with optional garnish such as fresh berries and/or chocolate shavings. Serve cake immediately or chill, uncovered, for up to 4-6 hours before serving.
Step 19
Cover leftover cake tightly and store in the refrigerator for 5 days.
Step 20
Save recipe for the next time?
Chef's notes
Make Ahead & Freezing Instructions:
Prepare cake through step 4. Wrap the individual baked and cooled cake layers tightly and refrigerate for up to 2 days or freeze up to 3 months.
You can prepare the chocolate mousse in advance. See step 5. You can also prepare the chocolate ganache ahead of time too. Refrigerate prepared ganache for up to 2-3 days.
Frosted cake freezes well, up to 3 months. Thaw overnight in the refrigerator, then bring to room temperature or serve cold.
Special Tools:
8-inch Round Cake Pans or 9-inch Round Cake Pans, Glass Mixing Bowl, Whisk, Electric Mixer (Handheld or Stand), Cooling Rack, Double Boiler, Cake Stand or Cake Turntable, Large Icing Spatula, Bench Scraper, Cake Carrier (for storage).
Espresso Powder/Coffee:
Espresso powder and coffee will not make the cake taste like coffee. Rather, they deepen the chocolate flavor.
