Use this frosting to make our Lemon Poppy-Seed Lady Cake.
In a small saucepan, combine 1 1/2 cups sugar with the corn syrup and 1/4 cup water. Place over medium heat, stirring occasionally until sugar has dissolved.
Raise heat, and bring to a boil, washing down sides of pan with a wet pastry brush to prevent crystals from forming. Continue boiling 5 to 7 minutes, or until a candy thermometer registers 230 degrees.
Meanwhile, in a mixing bowl, whisk egg whites on medium speed until soft peaks form, about 2 1/2 minutes. Gradually beat in remaining 1/4 cup sugar. Reduce speed to medium-low.
When syrup reaches 230 degrees, carefully pour it in a stream down side of bowl. Beat until frosting is cool, thick, and glossy, 5 to 10 minutes. Use immediately.