4 cups confectioners’ sugar (about 1 pound), sifted, plus more if needed 3egg whites
In a grease-free bowl combine 4 cups confectioners’ sugar and egg whites. Using clean beaters, beat on low speed. After 30 seconds, scrape down bowl with a rubber spatula and gradually increase speed to medium-high. Beat until icing is glossy and stiff peaks form when beaters are lifted, 5 to 7 minutes.
If icing is to be applied with a paint brush, stir in water, a few drops at a time, to achieve desired consistency. If icing is to be piped through a pastry bag fitted with a decorating tip, stiffen icing by stirring in more confectioners’ sugar.
The icing can be refrigerated in an airtight container for up to four days. Beat lightly with a fork before using.