Tiramisu cupcakes with marscapone buttercream and fondant hearts. Recipe for marscapone buttercream: 12 tablespoons unsalted butter, room temperature 8 ounces Mascarpone cheese, room temperature 4 cups confectioners sugar, sifted 1 tsp vanilla 1 TBSP kahlua Beat buffer and cheese until light and creamy. Add sugar and continue beating until smooth. You can make this frosting several days ahead and store lightly covered in the refrigerator. Bring to room temperature before using.