This is one I use.
Marshmallow Cream Filling (Twinkie Like)
Makes 1 1/2 cups.
2 teaspoons very hot water
rounded 1/4 teaspoon salt
1. Combine the salt with the hot water in a small bowl and stir until salt is dissolved. Let this mixture cool.
2 cups marshmallow crem (1 7-ounce jar)
1/2 cup shortening
1/3 cup powdered sugar
1/2 teaspoon vanilla
2. Combine the marshmallow cream, shortening, powdered sugar, and vanilla in a medium bowl and mix well with an electric mixer on high speed until fluffy.
3. Add the salt solution to the filling mixture and combine.