This recipes makes 3 cups of each flavor of frosting, if that ends up being more than you need to Neapolitan 1 dozen store-bought doughnuts, you can save the leftover icings for dipping other store-bought baked goods like brownies or crispy rice treats. The idea is to make the Neapolitan Icing flavors, then dip to your heart's content. (If you really want to get fancy, make one of our homemade doughnut recipes, let them cool while you prepare the frostings, and then dip them.)These icings will start to stiffen as they sit. They will be good for 1/2 hour after you mix them up. If you want to make them in advance and use them later, place them in a bowl and lay a damp paper towel directly on the surface. And then cover the bowl with plastic wrap and leave at room temperature. If necessary, whisk in an additional 1-2 Tbsp. hot water to recapture proper consistency.