- Stir sugar into espresso until dissolved. Set aside to cool.
- Using a long serrated knife, cut cake in half horizontally, making 2 layers. Place 1 layer in the bottom of a 9-inch square baking dish. Using a pastry brush, brush with half the espresso syrup. Sift 2 tablespoons espresso powder over top
- Put 1 quart ice cream into bowl of an electric mixer fitted with the paddle attachment. Mix on low speed until softened; spread over bottom cake layer. Top with second cake layer; brush with the syrup. Let chill in freezer 20 minutes
- Sift remaining 2 tablespoons ground espresso over cake. Mix remaining quart ice cream in the bowl of an electric mixer until softened. Spread over cake, swirling decoratively. Freeze until firm.
- Frozen tiramisu can be wrapped in plastic and stored in the freezer up to 3 days. Before serving, garnish with chocolate curls.