Chocolate Mousse Cake

Prep Time: 40 minutes | Cook Time: 30 minutes | Chill Time: 5 hours

Total Time: 6 hours 30 minutes

Yield: 8-10 slices

Nearly every month, my husband is in the kitchen concocting something delicious as a birthday baked-good treat for one of his employees. He asks what flavors they would like him to focus on, then either digs into his arsenal of delicious recipes or scours the internet for something new to try. This week, his employee Rebecca requested a decadent chocolate cake.

The recipe he found features a single layer of moist chocolate cake piled high with homemade, light, and fluffy chocolate mousse, all covered in a rich shell of chocolate ganache. I'm sure it will turn out to be the perfect treat for a very deserving employee.

Chocolate Cake Ingredients

Ingredients

Chocolate Cake

  • 3/4 cup (95g) All-Purpose 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

  • 1/2 cup (120g) Hot Coffee
  • 1 tbsp Dutch Process Cocoa Powder

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

  • 6 oz 70% Dark Chocolate, chopped
  • 3/4 cup (180g) Heavy Cream

Specialty Equipment

  • Spring Form Pan
  • Acetate Cake Collar

Instructions

Making the 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. Brown Sugar mixed with oil to ready for the dry ingredients.
  6. Then whisk in the eggs and vanilla, followed by the sour cream.
  7. 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.
  8. Pour the batter in the prepared pan.
  9. Bake for 25-30 minutes or until a toothpick in the center comes out clean with a few moist crumbs.
  10. Allow the cake to cool completely either at room temperature or in the refrigerator.
  11. Once cooled, remove the ring from the spring form pan and clean it off, you will need this again. Level off the top of the cake using a cake leveler or a large knife.
  12. Place the cleaned spring form ring back on the pan with the cake still inside.
  13. Now line the side of the pan with a long sheet of acetate (AKA a cake collar), sliding it down between the cake and the sides of the pan.
  14. *See notes for parchment paper option

Creating the 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.

Whipping up the Chocolate Mousse

    Chopped Dark Chocolate and Cream ready to be melted.
  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. Starting to incorporate the meringue into the melted dark chocolate slowly.
  13. Now we have our bowl of chocolate, a small bowl of whipped cream, and our large bowl of meringue (whipped egg whites + sugar).
  14. Using a rubber spatula, scoop the whipped cream into the chocolate mixture and gently fold to combine.
  15. 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.
  16. Pour the mousse over the chocolate cake and chill in the refrigerator for at least 4 hours but preferably overnight.

Making the Chocolate Ganache

    Unfortunately the pouring of the glaze was made difficult by the cooler temperature of the house and the ganache set a little too fast.
  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.

Slice and enjoy!

The end product of the Chocolate Mousse Cake.