Royal Icing: Sift 1 pound powdered sugar into a large mixing bowl. Add 6 tablespoons warm water, 3 tablespoons
powdered egg whites (see Recipe Tips above for egg-free option), and 1 teaspoon vanilla extract. Beat with an electric mixer on high for 5 to 7 minutes, or until stiff peaks form and the icing is fluffy and glossy. Spoon or pipe the icing onto cookies to decorate.