Classic French Mocha Opera Cake Recipe

mocha-opera-cake
Mocha Opera Cake. Christian Aludino / EyeEm - Getty Images
  • 110 mins
  • Prep: 80 mins,
  • Cook: 30 mins
  • Yield: 16 cake slices
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This delicious opera cake features all the same components as the traditional opera cake from Dalloyau, with one crucial exception: chocolate. The combination of alternating layers of espresso and rich chocolate make for a luscious, irresistible combination. A slice of this mocha opera cake is all one needs for a gorgeous showstopper of a dessert.

What You'll Need

  • Almond Cake:
  • 6 large egg whites, room temperature
  • 2 tablespoons granulated sugar
  • 2 cups ground blanched almonds
  • 2 1/4 cups confectioners' sugar, sifted
  • 6 large eggs
  • 1/2 cup all-purpose flour
  • 3 tablespoons butter, melted and cooled
  • Espresso syrup:
  • 1/2 cup water
  • 1/3 cup sugar
  • 1 1/2 tablespoons instant espresso
  • Coffee buttercream:
  • 2 tablespoons instant espresso
  • 2 tablespoons boiling water
  • 1 cup sugar
  • 3 tablespoons water
  • 1 teaspoon vanilla extract
  • 1 egg
  • 1 egg yolk
  • 14 tablespoons butter, at room temperature
  • Dark chocolate ganache:
  • 8 ounces bittersweet chocolate, finely chopped
  • 1/2 cups whole milk
  • 1/4 cup heavy cream
  • 4 tablespoons butter, at room temperature
  • Chocolate glaze:
  • 5 ounces bittersweet chocolate, finely chopped
  • 1/2 cup butter
  • ganache

How to Make It

To make the almond sponge cake:

Preheat the oven to 425F. Line two 15-inch by 12-inch pans with parchment paper and brush the surface of the paper with butter. Set them aside for a moment.

Using an electric beater, beat the egg white on high until they become foamy and start to expand. Sprinkle in the sugar, one teaspoon at a time, until all of it if incorporated into the egg whites. Continue beating the meringue until it is glossy and holds stiff peaks.

In a separate bowl, beat the ground almonds, confectioners' sugar, and whole eggs on medium just until the mixture becomes light and foamy. Gently stir the flour into the almond batter.

Gently stir 1/4 of the almond batter into the whipped egg whites. Fold the remainder of the almond batter and the melted, cooled butter into the egg whites. Divide the sponge cake batter between the two prepared pans and bake the cakes for 5 minutes, until the surfaces spring back from a light touch.

Cover the top surface of each cake with a fresh piece of parchment and carefully invert them onto a clean surface. Slowly peel back the old parchment from the cakes and allow them to rest loosely over the cakes to prevent them from drying out.

To make the espresso syrup:

In a small saucepan, set over medium heat, bring 1/2 cup water, 1/3 cup granulated sugar, and 1 1/2 tablespoons instant espresso to a boil. Allow the mixture to cool for 5 minutes. Set it aside to brush onto the cake later.

To make the chocolate  buttercream:

In a clean bowl, beat the butter on medium high speed for 5 minutes, until it turns light and fluffy. Lower the beater speed to low, and then add the remaining ingredients. Once the confectioners' sugar is completely incorporated, raise the beater speed to medium high and beat the frosting for 2 minutes, until it turns light and fluffy.

To make the ganache 

In a medium saucepan, set over medium heat, bring the milk and cream to a boil. Remove the pan from the heat and stir in the chocolate. Continue stirring the chocolate for 2 minutes, to insure a completely smooth texture. Stir in the butter and continue stirring the ganache for 90 seconds.

To assemble the cake:

Line a large baking sheet with parchment paper. Cut one 10-inch by 10-inch square out of each layer of cake and place it on the baking sheet. Brush the  first layer of cake with the espresso syrup. Carefully spread 3/4 of the chocolate buttercream over the surface of the cake.

Place the two spare rectangles of cake over the chocolate buttercream, and then brush them with espresso syrup. Spread the ganache over the cake in a smooth layer. Place the last layer of cake over the ganache, brush with espresso syrup, and then spread it with a thin layer of the chocolate buttercream. Chill the cake in the refrigerator for 1 hour before glazing it.

To glaze the cake:

Clarify the butter by boiling it and skimming off  and discarding the solids. Melt the chocolate in a double boiler and stir in the clarified butter until the glaze is smooth. Pour the chocolate glaze over the cake and allow it to set in the refrigerator bore serving.