Store the peanut butter buttercream frosting in an airtight container or wrapped tightly with plastic wrap in the fridge for 2 weeks or in the freezer for 3 months. Thaw buttercream by bringing it to room temperature and rewhipping for 5 minutes.
This recipe makes approximately 5-6 cups of frosting. This is enough to ice 3-4 dozen cupcakes or frost a 3-layer 7-inch, 8-inch, or 9-inch round cake.