Step 1 In the bowl of a stand mixer, or in a large bowl using an electric mixer, beat the egg whites and cream of tartar until the whites are fluffy and have formed soft peaks. With the mixer running, begin beating in the powdered sugar. Continue beating until all of the sugar has been added and the icing holds stiff peaks when the beater is raised. If not using immediately, cover the surface of the icing with plastic wrap to prevent it from drying and hardening.