Combine sugar, syrup, water, and salt in a heavy saucepan. Cook over medium heat, stirring constantly, until mixture is clear. Cook, stirring frequently, until mixture reaches firm ball stage (242°).
Beat egg whites (at room temperature) until soft peaks form; continue beating egg whites while slowly adding syrup mixture. Add vanilla; continue beating until stiff peaks form and frosting is thick enough to spread.
Oxmoor House Homestyle Recipes
