1-1/2 c. Sugar
2 Tbsp corn syrup
6 egg whites
In a heat proof bowl of an electric mixer, mix all ingredients (except vanilla) and place the bowl over a saucepan of simmering water.
Whisk the mixture until it reaches 160 degrees using a candy or instant read thermometer.
Transfer the mixing bowl to your mixer, and with the whisk attachment, beat on high until stiff, glossy peaks form (about 6 minutes).
Whip in the vanilla. Frost cake immediately.