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close up on a slice of chocolate mousse cake

Chocolate Mousse Cake


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5 from 18 reviews

  • Author: Jenna Barnard
  • Total Time: 6 hours 10 minutes
  • Yield: 8-10 slices

Description

This chocolate mousse cake is the definition of decadence! A single layer of moist chocolate cake is piled high with homemade light and fluffy chocolate mousse and the entire cake is covered in a rich shell of chocolate ganache. It’s the perfect treat for any special occasion and is sure to impress!


Ingredients

Chocolate Cake

  • 3/4 cup (95g) all-purpose flour (or gf baking flour)
  • 2 tbsp cornstarch
  • 1/4 cup (25g) dutch process cocoa powder
  • 1 tsp baking soda
  • 1/2 tsp baking powder
  • 1/4 tsp kosher salt
  • 1/2 cup (100g) fine granulated sugar
  • 1/2 cup (105g) dark brown sugar, packed
  • 1/2 cup (112g) vegetable or olive oil
  • 2 large eggs
  • 1 tsp vanilla extract
  • 1/2 cup (120g) sour cream
  • 1/2 cup (120g) hot coffee

Chocolate Cake Soak

Chocolate Mousse

  • 7 oz 70% dark chocolate, chopped
  • 7 oz milk chocolate, chopped
  • 3 large eggs, separated
  • 3 tbsp water
  • 1 1/2 tsp unflavored gelatin
  • 1 3/4 cup heavy cream, divided
  • 1/2 tsp cream of tartar
  • 1/4 cup (50g) fine granulated sugar

Chocolate Ganache


Instructions

Chocolate Cake

  1. Preheat the oven to 350F and grease the inside of a 9″ springform pan.
  2. Then remove the ring, lay a sheet of parchment paper on the bottom plate, and close the ring on top. Some paper will be sticking out of the sides.
  3. Now in a medium bowl, whisk together the flour, cornstarch, cocoa powder, baking soda, baking powder, and salt. Set aside.
  4. In a large mixing bowl, whisk together the sugar, dark brown sugar and oil. It should look like wet sand. 
  5. Then whisk in the eggs and vanilla, followed by the sour cream.
  6. Dump in the dry ingredients and mix until it’s halfway combined. Then pour in the hot coffee and mix until smooth. The batter will be very thin.
  7. Pour the batter in the prepared pan and bake for 25-30 minutes or until a toothpick in the center comes out clean with a few moist crumbs.
  8. Allow the cake to cool completely either at room temperature or in the refrigerator.
  9. Once cooled, remove the ring from the pan and clean it off. Then level off the top of the cake using a cake leveler or a large knife.
  10. Place the clean ring back on the pan with the cake still inside.
  11. Now line the pan with a long sheet of acetate (AKA a cake collar), sliding it down between the cake and the sides of the pan. *See notes for parchment paper option

Chocolate Cake Soak

  1. Stir together the hot coffee and cocoa powder.
  2. Spoon the mixture over the cake, evenly soaking the entire surface.
  3. Now set the cake aside while we make the mousse.

Chocolate Mousse

  1. Add the chopped chocolate to a heat safe bowl. 
  2. Fill a saucepan with about 1/2 inch of water and place over medium heat. Then place the heat safe bowl on top, ensuring it does not touch the water.
  3. Once simmering, the water below will slowly melt the chocolate. Stir until smooth then remove from heat. Allow the chocolate to cool slightly while you clean out the saucepan as we will be using it again. 
  4. After a few minutes, whisk 3 egg yolks into the chocolate mixture one at a time. The chocolate will thicken significantly, but that’s ok. 
  5. Now fill a tiny bowl with 3 tablespoons of water and sprinkle the gelatin on top. Let it sit while we heat the cream. 
  6. Pour 3/4 cup of heavy cream into the cleaned saucepan and place it over medium-low heat. Heat just until it’s steaming but not bubbling. 
  7. By now, the gelatin should have bloomed (AKA the powder has absorbed all the water and turned clear). Scoop the gelatin into the steaming cream and whisk to melt. 
  8. Remove from heat and pour half of the cream into the chocolate and egg yolk mixture. Whisk until smooth, then whisk in the rest of the hot cream. The chocolate mixture should now be smooth and glossy – almost like pudding. 
  9. Now in a large bowl using a hand or stand mixer with the whisk attachment, add the remaining 1 cup of heavy cream. Whip on high speed until light and fluffy with stiff peaks. 
  10. Scoop the heavy cream into a smaller bowl and clean out the big mixing bowl and whisk. Make sure both are spotless and completely dry.
  11. Now to that clean bowl, add the egg whites and cream of tartar. Whip on high speed. Once it starts to turns foamy and opaque, slowly whip in the fine sugar. Keep mixing on high speed until it turns white with soft peaks (pull the whisk away and if the meringue stands up with a little droop on the end, it’s perfect). 
  12. Now we have our bowl of chocolate, a small bowl of whipped cream, and our large bowl of meringue (whipped egg whites + sugar).
  13. Using a rubber spatula, scoop the whipped cream into the chocolate mixture and gently fold to combine. 
  14. When it’s well incorporated, scoop in the meringue and repeat the process. Keep folding until the mousse is all one color with zero white streaks. The mousse should also be somewhat thin and pourable. 
  15. Pour the mousse over the chocolate cake and chill in the refrigerator for at least 4 hours but preferably overnight. 

Chocolate Ganache

  1. When the mousse has set, release the ring from the pan and peel back the cake collar. 
  2. For the ganache, add the chopped chocolate to a medium-sized heat safe bowl and the heavy cream to a heat safe measuring glass. 
  3. Microwave the cream until it’s hot and bubbling. Pour the hot cream over the chocolate, ensuring the chocolate is completely submerged.
  4. Allow the mixture to sit for about 3 minutes, then whisk to combine. 
  5. Pour the glossy ganache in the center of the cake and use a spoon or small overset spatula to spread it out towards the sides, allowing it to drip down. 
  6. Chill the cake for at least 30 minutes to allow the ganache to set. Then slice and enjoy! 

Notes

*PARCHMENT PAPER – If you don’t have acetate available, you can also use parchment paper. Before returning the ring to the pan, give it a light spritz of nonstick spray. Then place the ring back on the pan and line the sides with long strips of parchment paper, allowing the paper to reach about an inch above the sides of the pan. Then when the cake has chilled, remove the ring and peel away the paper. This method isn’t as clean as the acetate but it will get the job done. 

  • Prep Time: 40 minutes
  • Chill Time: 5 hours
  • Cook Time: 30 minutes
  • Category: Dessert
  • Method: Baking
  • Cuisine: French
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