Using meringue powder (or powdered egg whites), instead of raw egg whites, eliminates food-safety concerns. Look for the powder at baking-supply stores and many supermarkets. Royal icing hardens quickly, so if not using immediately, transfer to an airtight container and store in the refrigerator, up to one week; before using, stir with a flexible spatula until smooth.

Ingredients

　　1 pound (4 cups) confectioners’ sugar, sifted

　　1/4 cup plus 1 tablespoon meringue powder

　　Scant 1/2 cup water, plus more as needed

　　With an electric mixer on low speed, beat all ingredients until smooth, about 7 minutes. If icing is too thick, add more water, a little at a time, beating until icing holds a ribbon on the surface for a few seconds when beater is lifted; if too thin, continue mixing 2 to 3 minutes more.

　　Martha Stewart's Cupcakes