Spread this delectable frosting on cookies and cakes, or just lick it off the spoon - we won't tell Santa.
Stir together eggnog and bourbon in a small bowl; set aside. Beat butter in a large bowl with an electric mixer on medium speed until light and fluffy. Gradually beat powdered sugar into butter alternately with eggnog mixture, beating until light and fluffy, adding additional eggnog 1 teaspoon at a time to reach desired consistency. Use immediately.