The powdered egg whites act as a stabilizer and allows the icing to harden. Make certain to purchase only POWDERED egg whites, powdered egg whites are available in the baking section of most major super markets. This is wonderful to decorate Christmas cookies such a gingerbread cookies, you can also pipe it through a pastry bag. Add in food colouring to create colours if desired. I have usd this recipe many times, it is wonderful for anything you want to decorate!