Start the recipe so it coincides with the cake/brownies coming out of the oven. Brownies/cake should be frosted as soon as it is removed from the oven, CAREFULLY! You will tear apart a hot cake so go slow and easy. Plop the icing on and spread, carefully, carefully.
1 stick butter
4 Tbsp Cocoa powder
6 Tbsp milk
1 lb powdered sugar
1 tsp vanilla extract
Melt butter in saucepan on low heat (not microwave). Add cocoa and milk to the saucepan, Stir/whip until mixture is combined and just bubbles, Remove from heat immediately. At this point, if necessary, transfer cocoa mixture to a bowl to accomodate the sugar. Beat in powdered sugar and then vanilla. (If your saucepan is big enough, simply mix it in the saucepan!)
Spread icing carefully onto brownies/cake within ten minutes of being removed from the oven. This is a careful process, maybe let the cake/brownie sit for a few minutes and then spread the icing. CAREFULLY!
Did I say that enough? It is hot and will tear. Plop it in several areas onto the cake and let it warm a bit, then distribute the icing around.