Cream butter and shortened with an electric mixer on medium until fluffy.
Gradually add the powdered sugar, about 1/2 cup at a time.
Add vanilla extract and mix.
Fold the marshmallow creme into the frosting until incorporated.
Notes
You can use butter instead of shortening, but shortening makes it more firm to be used in decorating.
Use up to 2 cups powdered sugar to make this frosting even stiffer so you can make flowers with details or stand our petals.
Makes enough to generously frost 24 cupcakes.
Variations
Make mocha marshmallow frosting by adding unsweetened cocoa powder and a bit of espresso powder when mixing in the confectioners sugar. Switch out the vanilla extract for almond for an amazing flavor or if you love it, use a little bit of both. Add softened cream cheese for a marshmallow cream cheese frosting.
Storage
Leftover marshmallow frosting can be stored in the refrigerator for up to a week or frozen for up to three months. Be sure to let it come to room temperature before piping onto your cupcakes or cake.