Time: 25 minutes. This recipe goes with our Best Butter Cake—but it's also great as a cookie frosting.
Melt chocolate in the top of a double boiler over simmering water. Let cool to room temperature, about 10 minutes. Add butter and beat on high speed with an electric mixer until light and fluffy, about 2 minutes. Add 3 cups powdered sugar and the milk; beat until smooth. Add more powdered sugar if frosting seems too thin.