I split a sponge cake into three layers, and filled it with this really simple buttercream. I hope you like it-we sure did. Because the filling is so sweet, I gave the outside of the cake a bit of lightly sweetened whipped cream, rather than a proper frosting. The combination seemed about right.
You will need:
2 cups sifted confectioner's/icing sugar
2 tablespoons unsweetened cocoa powder
1/2 teaspoon instant coffee
3 tablespoons melted butter
2-3 tablespoons cold water
Mix together, and beat until it reaches a spreading consistency. You may need more water if it is too thick.