Seven Minute Icing

Heating egg whites while beating denatures their proteins and creates a stable foam structure that traps air bubbles. The double boiler provides gentle, indirect heat that cooks the egg whites to a safe temperature (160°F) while preventing curdling. Meanwhile, the sugar dissolves completely in the water and egg white mixture, then stabilizes the foam as it cools, creating a glossy, marshmallow-like texture. The constant beating incorporates air and ensures even heat distribution, preventing the proteins from coagulating into scrambled eggs.