I usually double recipe. Then there is some extra leftover.

1 1/2 c. sugar
6 tbsp. butter
1/3 c. cocoa
1/3 c. milk

Mix in a saucepan. Boil 5 to 6 minutes for double recipe. (Boil 2 1/2 minutes for regular recipe.) Let cool. Beat. When the frosting begins to turn from glossy to dull, it is time to pour it on the cake. Very good.