1/2 cup butter or margarine
2 Tablespoons dark cocoa
1/4 cup milk
3 1/2 cups powdered sugar
1 teaspoon vanilla
In a saucepan, combine the butter, cocoa and milk. Stir and heat to boiling.
Mix in the powdered sugar and vanilla until frosting is smooth.
Pour warm frosting over brownies as soon as you take them out of the oven.
Cut into bars.