Photography: Jonathan Lovekin
- 1/2 stick unsalted butter, softened
- 1 1/2 cups confectioners' sugar
- 1/4 cup granulated sugar
- 2 teaspoons pure vanilla extract
- 1 to 2 tablespoons whole milk, if needed
Beat butter with a mixer on medium-high speed until light and fluffy, about 3 minutes. Reduce speed to low, and gradually add sugars, beating until thoroughly combined. Beat in vanilla. If filling is too thick to spread, beat in milk, 1 tablespoon at a time, until spreadable.