Heat oven to 350 degrees F (175 degrees C). Grease and flour 3 (9 inch) pans.
Cake: Prepare the cake mix according to package directions. Divide two thirds of batter
between 2 pans. Stir instant coffee into remaining batter; pour into remaining pan.
Bake in the preheated oven for 20 to 25 minutes, or until a wooden pick inserted
into the center of the cake comes out clean.
Let cool in pan 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
Filling: In a small bowl, using an electric mixer set on low speed,
combine mascarpone, 1/2 cup confectioners' sugar and 2 tablespoons coffee liqueur;
beat just until smooth. Cover with plastic wrap and refrigerate.
Frosting: In a medium bowl, using an electric mixer set on medium-high
speed, beat the cream, 1/4 cup confectioners' sugar and 2 tablespoons coffee
liqueur until stiff. Fold 1/2 cup of cream mixture into filling mixture.
Assemble the cake: Place one plain cake layer on a serving plate. Using a
thin skewer, poke holes in cake, about 1 inch apart. Pour one third of reserved
coffee mixture over cake, then spread with half of the filling mixture. Top with
coffee-flavored cake layer; poke holes in cake. Pour another third of the coffee
mixture over the second layer and spread with the remaining filling. Top with remaining
cake layer; poke holes in cake. Pour remaining coffee mixture on top. Spread sides
and top of cake with frosting.
Garnish: Place cocoa in a sieve and lightly dust top of cake.
Garnish with chocolate curls. Refrigerate at least 30 minutes before serving.