Tiramisu Cake

1. Preheat oven to 350 degrees F (175 degrees C). Grease and flour 3 (9-inch) pans.
2. Prepare the cake mix according to package directions. Divide two thirds of the batter between 2 pans. Stir instant coffee into remaining batter; pour into the remaining pan.
3. Bake in the preheated oven for 20 to 25 minutes, or until a toothpick inserted into the center of the cake comes out clean. Let cool in the pans for 10 minutes, then turn out onto a wire rack and cool completely. In a measuring cup, combine brewed coffee and 1 tablespoon coffee liqueur; set aside.
4. To make the filling: in a small bowl, using an electric mixer set on low speed, combine mascarpone, confectioners’ sugar and coffee liqueur. Beat just until smooth. Cover with plastic wrap and refrigerate.
5. To make the frosting: in a medium bowl, using an electric mixer set on medium-high speed, beat the cream, confectioners’ sugar and 2 tablespoons coffee liqueur until stiff. Fold 1/2 cup of cream mixture into the filling mixture.
6. To assemble the cake: Place one plain cake layer on a serving plate. Using a thin skewer, poke holes in the cake, about 1 inch apart. Pour one third of the reserved coffee mixture over the cake, then spread with half of the filling mixture. Top with coffee-flavored cake layer; poke holes in the cake. Pour another third of the coffee mixture over the second layer and spread with the remaining filling. Top with the remaining cake layer; poke holes in the cake. Pour remaining coffee mixture on top. Spread sides and top of cake with frosting. Place cocoa in a sieve and lightly dust the top of the cake. Garnish with chocolate curls. Refrigerate for at least 30 minutes before serving.
7. To make the chocolate curls, use a vegetable peeler and run it down the edge of the chocolate bar.