Food & Cooking Recipes Dessert & Treats Recipes Whoopie Pie Filling 3.2 (283) Close Yield: Makes 3 3/4 cups This delicious whoopie pie filling is courtesy of Cranberry Island Kitchens. Directions In the bowl of an electric mixer fitted with the paddle attachment, cream together butter and sugar until pale and fluffy, about 3 minutes. Add Fluff and vanilla and continue mixing until well combined.