Heat 1 1/2 cups sugar, the water, and corn syrup in a medium saucepan over medium heat, stirring until sugar dissolves. Increase heat; bring to a boil. Wash down sides of pan with a wet pastry brush to prevent sugar crystals from forming. Cook until it registers 235 degrees on a candy thermometer.Advertisement
Meanwhile, whisk egg whites with a mixer on medium speed until soft peaks form, about 2 minutes. Add the remaining 1/4 cup sugar; reduce speed to medium-low. Pour the hot syrup into the egg-white mixture in a slow, steady stream. Increase speed to medium high; beat until stiff peaks form, about 7 minutes. Beat in vanilla; use immediately.