We like frittatas for a couple reasons. First, they are very tasty. Second, they make great leftovers. They are easy to make and your imagination is your guide for the components. This particular one had onions, pork sausage, mushrooms and swiss cheese. I figure they are done when they no longer jiggle and they are very slightly pulling away from the side of the pan. After removing from the oven I let them sit for a while to firm up then transfer them to a large plate in one piece for serving. I like mine with a large dose of picante sauce.