Well, some will argue in the truest sense it is merely a matter of one being an egg mixture folded around a filling and the other, served open-faced with the ingredients mixed into the egg. And regardless of whether or not you agree with that philosophy – as more than a few establishments serve the open-faced variety and mistakenly or willfully deem it an omelet – there are a few other factors that separate the two as well.
For one, omelets are usually cooked quickly on a stovetop. The ingredients, although sometimes mixed into the egg itself, are usually added once the egg begins to cook and is firm enough to fold over the added ingredients.
On the other hand, frittatas are cooked more slowly with the ingredients and egg blended together. And most often, cooking begins on a stovetop and is finished in an oven or under a broiler.
From that point onward, all goes to hell in a hand basket. You see, the banter pertaining what designates a frittata and what designates an omelet spirals out of control mainly because it tends to tread upon the ground of "personal preference", which we all know is a major no-no (except in the case of requesting mayonnaise on a prosciutto and mozzarella sandwich in an Italian deli; in which case, personal preferences are denied and the request itself could be grounds for permanent expulsion).
For instance, I've heard it said that frittatas are well-cooked, while omelets are traditionally served wet.
That may be true traditionally, but if so, why would “runny”, “wet”, “firm” or “stiff” eggs even be an option at most restaurants? While I personally prefer my eggs one step above pourable, I know many folks who wouldn't touch a loose egg with an extension ladder. So the "well-cooked vs. wet" theory doesn't hold water with me.
Look, I may like my eggs where I can eat them with a straw, but I will never eat them after they've been sitting an hour at room temperature. You want to feed me a frittata, feed me one right out of the oven. Period. That's another theoretical difference that goes down the drain with me.
But taking everything into account, there is one other difference that cannot be disputed – Omelets are French. Frittatas are Italian. I, being of pure Italian lineage, will be making a frittata tonight. Ciao.
For an 8"-10" Frittata
1. Preheat oven to 450º
2. Crumble the sausage and cook until browned. Drain and set aside.
3. While sausage cooks, whisk eggs thoroughly with a splash of milk and set aside.
4. In a cast-iron pan (I prefer cast-iron because it distributes heat evenly and allows the egg to release easily), add onions, bell pepper, mushrooms and garlic, and cook over medium-high heat until they just start to soften.
5. Season with parsley, salt, pepper and crushed red pepper.
6. Add sausage back to the mix and allow just enough time for it to warm.
7. Spread the ingredients into an even layer along the bottom of the skillet and sprinkle with an even coating of cheese.
8. As the cheese just starts to melt, pour eggs over vegetables, sausage and cheese. Tilt skillet to allow the eggs to settle evenly within the nooks and crannies. Cook for a minute or two until the edges of the egg begins to set.
9. Put the entire cast-iron skillet into the oven and bake for approximately 12 minutes or until eggs are set.
10. Let cool for a few minutes before slicing and serving.