An omelet (also spelled omelette) is a dish of beaten eggs cooked in a pan until just set, typically folded around a filling or served plain. Egg dishes cooked this way have roots in ancient Persia, though the French word omelette is what gave the dish its modern name and its association with French technique. To make one, eggs are whisked, sometimes with a little milk, cream, or water, then poured into a lightly buttered pan over medium heat; as the edges set, they're pushed toward the center so the egg cooks evenly, and the finished omelet is folded in half or rolled. French-style omelets are cooked quickly for a light, barely-set, almost soufflé-like center, while American and Spanish versions, such as the potato-and-onion Spanish tortilla, are cooked longer into a thicker, fully-set, more heavily filled dish. Common fillings include cheese, mushrooms, onions, peppers, spinach, ham, bacon, or sausage.