In a large saucepan, heat whipping cream and butter over medium heat. Bring mixture to a simmer, stirring constantly. Remove pan from heat.
Add white baking pieces. Stir until melted and smooth. Stir in marshmallow creme.
Transfer mixture to a fondue pot, chafing dish, or ceramic bowl. Serve with assorted dippers. Can hold in a fondue pot for up to 1-1/2 hours, stirring occasionally. Makes 4 cups (sixteen 1/4-cup servings).