For cake layers 3 ounces fine-quality semisweet chocolate such as Callebaut 1 1/2 cups hot brewed coffee 3 cups sugar 2 1/2 cups all-purpose flour 1 1/2 cups unsweetened cocoa powder (not Dutch process) 2 teaspoons baking soda 3/4 teaspoon baking powder 1 1/4 teaspoons salt 3 large eggs 3/4 cup vegetable oil 1 1/2 cups well-shaken buttermilk 3/4 teaspoon vanilla
Special equipment two 10- by 2-inch round cake pans
PreparationMake cake layers:
Preheat oven to 300°F. and grease pans. Line bottoms with rounds of wax paper and grease paper. Finely chop chocolate and in a bowl combine with hot coffee. Let mixture stand, stirring occasionally, until chocolate is melted and mixture is smooth.
Into a large bowl sift together sugar, flour, cocoa powder, baking soda, baking powder, and salt. In another large bowl with an electric mixer beat eggs until thickened slightly and lemon colored (about 3 minutes with a standing mixer or 5 minutes with a hand-held mixer). Slowly add oil, buttermilk, vanilla, and melted chocolate mixture to eggs, beating until combined well. Add sugar mixture and beat on medium speed until just combined well. Divide batter between pans and bake in middle of oven until a tester inserted in center comes out clean, 1 hour to 1 hour and 10 minutes.
Cool layers completely in pans on racks. Run a thin knife around edges of pans and invert layers onto racks. Carefully remove wax paper and cool layers completely. Cake layers may be made 1 day ahead and kept, wrapped well in plastic wrap, at room temperature.
Chocolate mousse: 130 gr. Bittersweet chocolate 1/3 cup milk 2 heaped tablespoons Nutella spread 1 1/2 teaspoon gelatin powder 3 tablespoons milk 375 ml. heavy whipping cream
White chocolate mousse: 160 gr. White chocolate 1/3 cup milk 1 1/2 teaspoon gelatin powder 3 tablespoons milk 375 ml. heavy whipping cream
Chocolate topping: 150 gr. Bittersweet chocolate 150 ml. heavy cream
Make the dark chocolate mousse:
combine the gelatin and 3 tablespoons of milk in a little bowl, let rest for 10 minutes. Meanwhile, melt the chocolate and the 1/3 cup of the milk, add the Nutella paste and combine. Put the gelatin mixture in the microwave for 30 seconds, combine until smooth, and add to the chocolate mixture. Whip the cream, and fold it into the chocolate mixture. Pour the mousse onto the base, and freeze for an hour.
Make the white chocolate mousse:
combine the gelatin and 3 tablespoons of milk in a little bowl, let rest for 10 minutes. Meanwhile, melt the white chocolate and the 1/3 cup of the milk. Put the gelatin mixture in the microwave for 30 seconds, combine until smooth, and add to the white chocolate mixture. Whip the cream, and fold it into the white chocolate mixture. Pour the mousse onto the dark chocolate mousse layer, and freeze for an hour.
Make the chocolate topping: heat the cream nearly to its boiling point, pour it onto the chocolate and wait for a couple of minutes, then stir until the chocolate melts totally. Pour the chocolate topping onto the mousse, and freeze overnight, covered.
About 4 hours before you want to serve the cake, put it out of the freezer, and let it defrost in the refrigerator. Keep in the refrigerator