• Preheat oven to 350F and prepare the Twinkie pan or cupcake pan.
• In a large bowl or stand mixer whip 4 large egg whites until stiff peaks form.
• In a separate mixing bowl mix the cake mix with water. Fold the whipped egg whites into the batter and pour into the molds, filling halfway. Place extra batter in cupcake molds.
• Cake until the cake is golden brown and the cake bounces back when poked with a toothpick, around 18 minutes. Let cool for 10 minutes, remove from the molds, and then cool to room temperature.

Make the Filling

• In a medium bowl, whip together the marshmallow fluff, butter, confectioners sugar, and vanilla extract. Place the mixture in a piping bag with a tip or in a plastic bag with the tip cut off. Poke three holes in the cooled cake with a chopstick and fill the cake