Cream butter in the bowl of an electric mixture until completely smooth and creamy. With the mixer on low speed, add in powdered sugar slowly. Gradually increase mixer speed and add vanilla, then beat for 2-3 minutes, scraping down sides and bottom of the bowl. If frosting is too thick, add milk 1 teaspoon at a time until desired consistency is reached If it’s too thin, add sugar gradually until it thickens. Frost cupcakes and top with sprinkles.