For the Chocolate Buttercream Frosting:
Melt butter. Stir in cocoa powder. Alternately add powdered sugar and milk, beating to spreading consistency.
Add a small amount of additional milk if needed to thin the frosting, or a little extra powder until you reach your desired consistency. Stir in vanilla.
Cake Assembly:
Place one of the cake rounds on your serving stand or plate.
Smooth a thin layer of chocolate frosting over the cake layer, and then spoon half of the coconut frosting on top, spreading it into a smooth layer. Leave about 1/2 inch between the filling and edge of cake.
Stack the second cake round on top. Smooth chocolate frosting over the entire cake.
Spoon remaining coconut frosting on top of the cake.
