"This frittata is different from most because the egg whites are stiffly beaten before adding the egg yolks, creating a beautiful light and puffy golden edge/crust. Use the vegetables and cheese of your choice. It's based on a recipe in Martha Stewart's Everyday Food magazine. She suggested leeks, grape tomatoes and crumbled goat cheese, but we used onion, garden tomatoes and light cheddar, and it was fabulous...."