As anyone (including Wikipedia) can tell you, a frittata is a recipe featuring beaten eggs that's cooked either on the stovetop or baked in the oven.
Sometimes it's referred to as an "omelet," which I'm afraid does injustice to both frittatas AND omelets, by failing to satisfactorily capture anything essential about either one. Is every frittata an omelet? Is every omelet a frittata?
Obviously not. Let's break down the frittata's essential characteristics one by one.
1. A Frittata is Round
I know, I know. You disagree, you protest, you're picketing my house, etcetera. Listen, though:
Yes, technically a frittata does not need to be cooked in a round pan. I've had wonderful frittatas that were baked in deep, rectangular roasting pans. And if you're preparing frittatas for a large number of people (like commercial kitchen quantities), that would certainly be the way to go.
You could, for instance, make a frittata in a rectangular casserole dish, with the major drawback being that you can't heat a casserole dish on the stovetop. You'd need to cook whatever other ingredients are going in the frittata in a separate pan before adding them to the egg mixture.
That's because you don't want a watery frittata. Veggies like tomatoes, mushrooms, onions, pretty much ANY vegetables, contain significant amounts of water, and if you add raw veggies to a frittata, that water will ooze out and turn your frittata into a sort of swampy mess.
That's why we cook our ingredients first, and we might as well do it in the same pan we're going to cook the eggs in. And since frittatas are often finished in the oven or even under the broiler, you need some form of cookware that's safe for both the stovetop and oven.
Guess what you've just described? Yes, a cast-iron skillet. And what shape are most cast-iron skillets? OK, you get the point.
So does a frittata need to be round? No. But is it quintessentially round? Absolutely. Just like pizza. There's nothing in the physical or metaphysical universe that prevents a pizza from being cooked on a rectangular pan. But pizza is round. Furthermore, its characteristic roundness necessarily gives birth to its archetypal wedge-shaped individual portion.
Just like the frittata.
So a frittata is an egg recipe cooked in a round pan of some kind and then cut into wedge-shaped servings.
2. A Frittata is Something You Make for a Large Group
There's no such thing as a frittata for one. A frittata is something you make when you want to feed a large group of people.
To make a frittata in a 12-inch cast-iron skillet, you're going to use a dozen eggs. That leaves room for other ingredients. Potatoes and mushrooms and cheese are heavenly, and so is spinach.
As such, a frittata is a great way to use leftovers, so it's a perfect breakfast or brunch item for the morning after a big holiday dinner, when you've got a house full of people and a fridge full of leftovers from the night before.
But the point is, have you ever eaten leftover eggs? No, and there's no way you're going to make a 12-egg frittata for fewer than six people. Plus, when you get around to slicing it, you'll find that the easiest and most natural way of doing it is into eight slices. (Just like a pizza.) Thus eight servings.
So we've identified another of a frittata's essential qualities: It's something you make for a large group. Like six to eight people.
3. A Frittata is Deep
We're beginning to put some distance between frittatas and omelets. An omelet, you know, is a flat sort of egg pancake, and depending on how you make yours, it might have some of its ingredients cooked into the egg itself, or they might be spooned across the middle before the whole thing gets folded in half.
But the fact that it's folded should be your clue. An omelet is an envelope made out of eggs. It's got its fillings neatly tucked inside like a tidy little parcel, and then folded down the middle, or maybe even into thirds. Which means it's thin. You fold a sheet of paper. But you don't fold a whole phone book.
(FYI, a phone book used to be this huge book full of the names and addresses of everyone in your whole town. It was a thick book. You couldn't fold it to save your life.)
And you don't fold a frittata, either. It's too thick. It's the phone book of egg recipes.
A cast-iron skillet is two inches deep, which means a frittata is about eight times thicker than a normal omelet. You can fill those two inches up with sliced potatoes, sausages, leeks, whatever, then pour your egg mixture over them and cook it. It's deep. If it were a pizza, it would be deep-dish. (Shout-out to all my Chi-town peeps.)
Which brings us, at long last, to the single most mind-blowing realization about frittatas.
4. A Frittata is a Custard
OMG you guys, it's really true. A custard is made by blending eggs with cream (or milk), and then gently cooking it until it sets.
And a frittata is: made by blending eggs with cream and then gently cooking it until it sets!
Think for a moment about crème brûlée. It's a mixture of eggs and cream baked in a dish with straight sides. It's done when the edges are set while the centers jiggle a little bit when you give them a nudge.
Well guess how you cook a frittata: You cook it gently until the edges are set and the center just barely jiggles when you nudge it.
And yes, the cream is a crucial ingredient. Without even a relatively small amount — like half a cup per dozen eggs — your frittata will be eggy and rubbery rather than smooth and creamy.
The ratio of egg-to-cream is different, and a frittata is savory instead of sweet, but the cooking principle is the same.
And So We Have Our Answer:
What is a frittata? A frittata is a round, deep, savory custard, that you make for a large group of people, and serve in wedge-shaped slices. Here's a yummy frittata recipe.