Double Boiler 7-Minute Frosting
["2 egg whites (1/4 c.)", "1 1/2 c. sugar", "1/4 tsp. cream of tartar or 1 Tbsp. light corn syrup", "1/3 c. water", "1 tsp. vanilla"]
["Combine egg whites, sugar, cream of tartar and water in top of double boiler.", "Beat on high speed 1 minute with electric mixer. Place over boiling water (water should not touch bottom of pan); beat on high speed 7 minutes.", "Remove pan from boiling water.", "Add vanilla.", "Beat 2 minutes longer on high speed."]
["egg whites", "sugar", "cream of tartar", "water", "vanilla"]