Browning the butter gives this icing a nutty flavor. The consistency should be thin enough to spread but not runny.
Source: Martha Stewart Living, November 1998
Yield Frosts 1 nine-inch cake
4 tablespoons unsalted butter
1 cup sifted confectioner's sugar
1 teaspoon pure vanilla extract
1 to 2 tablespoons milk
In a small saucepan, melt butter over medium-high heat until nut-brown in color, about 10 minutes. Remove pan from heat, and pour butter into a bowl, leaving any burned sediment behind.
Add sugar, vanilla, and 1 tablespoon milk; stir until smooth. If the icing is too thick, add the remaining tablespoon milk, a little at a time, until consistency is spreadable. Let cool 5 minutes. Use immediately.