Combine sugar, corn syrup, and hot water. Heat, stirring until sugar dissolves. Then boil, without stirring, to firm ball stage (244 to 248 on candy thermometer). Beat egg whites to stiff peaks. Slowly add hot syrup, ebating at high speed until thick and fluffy. Add salt and vanilla. Gently fold in mayonnaise or orange rind. If thicker than desired, fold in 1 or 2 Tblsp mayonnaise, or 1 or 2 tsp water. Keep refrigerated until served.
makes about 3 cups