Excellent! Great on brownies, too.
1/2 cup butter
1 cup granulated sugar
1/4 cup milk
2 cups, or more, pwd sugar
1 tsp vanilla extract
In a saucepan, melt the butter. Add granulated sugar and milk, stir until blended. Bring to a boil, stirring constantly. Remove from heat and cool. Gradually add enough pwd sugar to reach desired consistency. Add vanilla and stir well.
Fills and frosts 2 (8 or 9") cake layers, or a 9 x 13" cake.