Step 1

Place marshmallow creme, peanut butter, butter, and vanilla in a medium-sized mixing bowl. Mix at low speed with an electric mixer until well combined.

Step 2

Add confectioners' sugar and 1 tablespoon milk; beat at medium speed until just combined and smooth.

Step 3

Check consistency of frosting. If needed, beat in 1 more tablespoon milk to make frosting a nice consistency for spreading.

Step 4

Do not overbeat the frosting, because overbeating can make it runny.

Step 5

This recipe makes enough frosting to frost one sheet or 2-layer cake, or 20-24 cupcakes.