BOILED FROSTING

This is a classic Italian meringue where hot sugar syrup 'cooks' the egg whites, creating a stable foam that won't weep or deflate. The sugar syrup reaches the 'thread stage' (230-235°F), which denatures the egg proteins while the heat pasteurizes them. Adding hot syrup to beaten whites creates smaller air bubbles and stronger protein networks, while the extended beating (30 minutes) fully incorporates air and allows the mixture to cool and stabilize, resulting in a glossy, marshmallow-like frosting that sets firm without being brittle.