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Chocolate Mousse Gateau


Chocolate Mousse Gateau
Used under License from iStock
This cake is a little more complicated than a standard chocolate layer cake but the extra effort is well worth it. This delicate creation is a tender chocolate mousse cake filled with creamy rich pastry cream. It is lovely for any event but is perfect for an elegant gathering.

Prep Time: 5 hours

Cook Time: 25 minutes

: 6 hours

Total Time: 11 hours, 25 minutes

Yield: One four layer cake


  • Mousse Cake

    • 1 1/2 cup icing sugar
    • 1 cup good quality cocoa powder
    • 4 Tbsps. cornstarch
    • ¼ tsp. salt
    • 1 1/2 cup unsalted butter
    • 8 large eggs, separated at room temperature
  • Pastry Cream

    • 2 cup milk
    • 1 cup granulated sugar
    • 4 Tbsps. Cornstarch
    • 4 egg yolks
    • 1 vanilla bean
    • 2 Tbsps. unsalted butter
    • Pinch salt
  • Chocolate Satin Icing

    • 1 cup unsalted butter
    • 10 ounces semi-sweet chocolate
    • 6 ounces unsweetened chocolate
    • 3/4 cup heavy cream
    • 3 cups icing sugar
    • 4 tsps. pure vanilla extract


  1. Preheat oven to 325 degrees F
  2. Butter and flour the bottom and sides of two eight inch round cake pans.
  3. Line both pans with parchment rounds.
  4. In a small bowl combine 1 1/2 cups icing sugar with the cocoa, cornstarch and salt and then sift to remove any lumps.
  5. In a large bowl cream butter until light and fluffy, approximately three minutes.
  6. Add yolks to creamed butter one at a time beating well after each addition.
  7. Add cocoa mixture to the butter mixture one tablespoon at a time beating each time until very smooth.
  8. In a clean medium bowl beat egg whites until frothy.
  9. Slowly add remaining icing sugar by tablespoons beating until stiff and shiny.
  10. Gently fold the egg white mixture into chocolate mixture until it is fully incorporated.
  11. Transfer batter to pans and tap the pans to remove any trapped air.
  12. Line the outside of the pans with foil and place the pans in a large baking pan.
  13. Fill the large pan with enough hot water to come approximately halfway up the sides of the cake pans.
  14. Place the baking pan in the oven and bake approximately 25 minutes.
  15. Remove the pan from the oven and take the cake pans out of the larger pan and put them onto racks to cool.
  16. Put cooled cakes into the fridge and chill for at least four hours.

Pastry Cream

  1. Pour milk into a medium sauce pan and place over medium high heat.
  2. Slice the vanilla bean in half and scrape the seeds into the milk.
  3. Add the vanilla bean halves to the milk and heat milk until steamy.
  4. In a large bowl whisk egg yolks, cornstarch and sugar until completely combined and set aside until milk is hot.
  5. Remove the vanilla pod from the hot milk and pour the milk into the egg yolk mixture.
  6. Whisk to combine and strain mixture back into the saucepan.
  7. Place the sauce pan back on low heat and whisk until pastry cream thickens.
  8. Continue cooking, whisking constantly, for at least four more minutes and remove from the heat.
  9. Stir in butter and salt.
  10. Transfer pastry cream to a bowl and cover the surface directly with cling wrap, pushing the plastic down onto the top.
  11. Place in fridge and chill completely approximately two hours.


  1. Melt the butter and chocolates in a large bowl placed over gently simmering water, whisking constantly.
  2. Remove mixture from the heat and whisk in the heavy cream.
  3. Add icing sugar in four batches whisking after each addition until all the sugar is well incorporated.
  4. Whisk or stir in vanilla until the icing is very smooth
  5. Set icing aside covered until it is needed for the cake
  6. Take cakes out of the fridge when it is cooled and unmold the cakes from the pans.
  7. Peel the parchment paper off the bottom of the cakes.
  8. Place cakes right side up and level off the tops with a sharp serrated knife.
  9. Cut the cakes in half horizontally to create four layers and place first layer on a cake board.
  10. Fill a piping bag with the prepared chocolate icing with a large round tip or just the coupler in place.
  11. Pipe a circle of icing all around the edge of the cake layer to create a dam for the pastry cream.
  12. Spoon one third of the prepared chilled pastry cream into the center of the icing circle and spread the cream to the edges.
  13. Top the first iced cake layer with the second layer pressing down gently to create a seal.
  14. Repeat the filling process for the second and third layers and top with the last layer.
  15. Chill the cake for at least an hour to set the icing
  16. Frost the outside of the cake with the leftover chocolate icing and decorate with the desired cake decorating technique.

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