- 6 sticks unsalted butter, softened
- 9 cups confectioners' sugar
- 1 1/2 teaspoons pure vanilla extract
Beat butter and 3 cups sugar with a mixer on medium speed until combined. Reduce speed to medium-low, and continue to beat, gradually adding remaining 6 cups sugar, 1 cup at a time. Raise speed to medium-high; add vanilla. Beat until pale and fluffy, about 3 minutes more.
SourceMartha Stewart Living, September 2010