Icing For Sugar Cookies
["3 c. powdered sugar", "1/4 tsp. cream of tartar", "dash of salt", "2 tsp. vanilla", "2 egg whites"]
["Beat egg whites until very stiff.", "Add 1/2 of powdered sugar slowly.", "Add vanilla, salt and cream of tartar.", "Add remaining powdered sugar.", "Spread on cookies."]
["powdered sugar", "cream of tartar", "salt", "vanilla", "egg whites"]