This classic frosting is beaten for seven minutes in a double boiler. Due to its marshmallow-like consistency, be sure your cake is completely cooled before you frost it.
1 In the top of a double boiler, combine the sugar, egg whites, corn syrup, water and vanilla. Place over boiling water and beat with an electric mixer on high speed for 7 minutes, or until frosting forms peaks when beaters are raised. Remove from heat. Use immediately to frost a cooled cake.