Beat egg whites in large bowl with mixer at medium speed until frothy. Increase to high speed and beat just until soft peaks form (do not overbeat); set aside.
Stir corn syrup, water and sugar in a small saucepan. Cook over medium heat, stirring frequently until mixture boils. Cover and boil 2 minutes without stirring. Remove lid and boil 4 to 5 minutes longer. Remove from heat.
Beating egg whites on high speed, pour hot syrup in a thin, steady stream into egg whites, being careful not to pour syrup onto beaters. Add salt; continue beating until mixture is stiff and glossy. Beat in vanilla.
Gradually whisk sifted cocoa into egg white mixture, just until incorporated. Frost cake immediately or store frosting in airtight container in refrigerator for 2 days. (Frosting will gradually soften and deflate over time.)
About Corn Syrup
See why there’s no substituting Karo® Corn Syrups for treats with a delicate sweetness and smooth texture
Beat egg whites in large bowl with mixer at medium speed until frothy. Increase to high speed and beat just until soft peaks form (do not overbeat); set aside.
Stir corn syrup, water and sugar in a small saucepan. Cook over medium heat, stirring frequently until mixture boils. Cover and boil 2 minutes without stirring. Remove lid and boil 4 to 5 minutes longer. Remove from heat.
Beating egg whites on high speed, pour hot syrup in a thin, steady stream into egg whites, being careful not to pour syrup onto beaters. Add salt; continue beating until mixture is stiff and glossy. Beat in vanilla.
Gradually whisk sifted cocoa into egg white mixture, just until incorporated. Frost cake immediately or store frosting in airtight container in refrigerator for 2 days. (Frosting will gradually soften and deflate over time.)