Great for Brownies... this recipe is from my days in Home Ec... long ago!
In saucepan (yeah, that's what we called them back then!)
4 TBSP butter
1/4 cup cocoa powder
1/4 cup buttermilk
Bring to a boil ... mixture may appear slighly curdled.
Remove from heat
Stir in 1 tsp vanilla
2 1/4 cups sifted powdered sugar
IMMEDIATELY pour over brownies, spreading to the edges.