Red Velvet whoopies pies with cream cheese & marshmallow fluff filling Use one box of red velvet cake mix, add three eggs, 1/2 cup water and 1/2 cup oil. Mix well. Pipe heart shapes onto parchment paper (you can trace the heart shape on the parchment using a cookie cutter and then flip it over if you need a guide). Bake at 400 for 5-7 minutes. Fill with a mixture of 1/4 cup butter, 8 oz cream cheese, 1 jar fluff (7 oz) and 2 cups powdered sugar. Enjoy!