Preheat the oven to 325°F. Spray brownie pop molds or a mini cupcake tray with cooking spray and set aside.

Combine the pound cake mix and water in a bowl. Mix on medium speed with a standing or hand mixer for two minutes until well blended.

In a separate bowl, beat the egg whites on high speed until stiff peaks form. Fold the egg whites into the cake mixture and stir on low until well blended.

Fill the cavities of the brownie molds and/or cupcake tray two-thirds full with batter. Bake for 12 to 15 minutes, or until a toothpick inserted comes out clean and the top springs back when pressed. Let the cakes cool.

Combine the butter, confectioner’s sugar, marshmallow fluff and milk until well blended. Fit a disposable decorating bag with a size 10 tip. Fill the bag with the icing and close tightly with a rubber band.

Insert the tip into the bottom of a cake and squeeze frosting into the cake until it begins to ooze back out. If desired, scoop out some cake first with a toothpick to give the filling more room.