6 tablespoons butter
1 1/2 cups confectioners’ sugar
1/8 teaspoon salt
1 jar marshmallow creme (about 7 oz)
1 teaspoon vanilla
Food coloring (optional)
In a large bowl beat butter with an electric mixer until creamy. Add sugar and the salt to the butter; mix well. Add marshmallow creme and vanilla; blend well. If desired add food coloring. Use immediately to fill whoopie pies or refrigerate covered up to 1 week. Bring back to room temperature and lightly beat before using.
Makes 2 1/2 cups filling, enough to fill 12 whoopie pies.