This is a great recipe that I found recently from Martha Stewart’s Cupcakes book.
FLUFFY VANILLA FROSTING makes about 4 cups
1 1/2 cups butter, softened
1 pound (4 cups) confectioner’s sugar
1/2 tsp. pure vanilla extract
With an electric mixer, beat butter on medium-high speed until pale and creamy, about 2 minutes.
Reduce speed to medium. Add the confectioners’ sugar, 1/2 at a time, beating well after each addition and scraping down sides of bowl as needed; after every two additions, raise speed to high and beat 10 seconds to aerate frosting, then return t0 medium. This process should take about 5 minutes. Frosting will be very pale and fluffy.
Add vanilla, and beat until frosting is smooth. If not using immediately, frosting can be refrigerated up to 10 days in an airtight container. Before using, bring to room temperature, and beat on low speed until smooth again, about 5 minutes.