Chocolate Cream Cake

Instructions

To make the cake:

1. Preheat oven to 375°. Grease an 18"x 12" half-sheet pan. Line with parchment paper. Grease paper and dust with flour, tapping out excess.
2. Place chocolate in a microwave-safe bowl. Heat at half-power in microwave in 30-second increments until chocolate melts when stirred.
3. Add espresso to melted chocolate, and stir until smooth. Set aside to cool slightly.
4. Using an electric mixer on high speed, beat egg yolks until pale (2 to 3 minutes). Reduce mixer speed to medium and gradually add 1/3 cup sugar.
5. Increase mixer speed to high and continue beating until thick and pale (about 5 minutes). Reduce mixer speed to low, and add vanilla and chocolate mixture. Beat until blended.
6. In a separate bowl, beat egg whites, cream of tartar, and salt at high speed until soft peaks form. Gradually add 1/3 cup sugar, and continue beating until stiff and glossy.
7. Stir flour into chocolate mixture. Carefully fold the egg white mixture into the chocolate mixture.
8. Spread the batter evenly in prepared pan.
9. Bake 12 minutes, or until cake has risen and is slightly springy. Place pan on a wire rack to allow cake to cool completely.
10. If necessary, run the top of a knife around the cake to loosen the edges. Sift cocoa powder over the surface of the cake.
11. Cover the cake with wax paper, top with a large cutting board, and invert the cake. Remove the pan and parchment paper. Cut cake in half crosswise to form two rectangles.
12. Chill cake 30 minutes, or until firm.

To make the topping:

1. Place butter, sugar, and water in a small saucepan. Bring to a boil over medium-high heat.
2. Remove from heat and add bittersweet and unsweetened chocolates. Allow to stand for 2 minutes. Then, add vanilla and stir until mixture is smooth.
3. Allow to cool for 30 minutes, or until slightly thickened.

To make the filling:

1. Place chocolate, butter, and water in a small saucepan. Cook over low heat, stirring constantly, until smooth and thoroughly combined. Transfer mixture to a small bowl and allow to cool.
2. Using an electric mixer with a whisk attachment, beat cream until it begins to thicken. Sprinkle confectioners' sugar and vanilla over cream. Continue beating until soft peaks form.
3. Gently fold whipped cream into cooled chocolate mixture.

To assemble:

1. Spread the filling over one half of the cake.* Place the other half of the cake, cocoa side up, on top of the filling. Press down lightly. Use an off-set spatula to smooth the edges.
2. Pour the topping over the top of the cake. Gently spread the topping evenly over the top of the cake.
3. Place cake in freezer for 4 hours or overnight.**
4. Allow cake to sit at room temperature until soft enough to cut. Cut into squares and serve.