Farmers Market Frittata. (Scott Suchman/For The Washington Post)

Every cook needs a frittata to call his or her own. A chubby, big-as-a-plate, well-done omelet with a generous amount of add-ins, the frittata is a cook’s tabula rasa and a host’s best friend.

Known as a tortilla in Spain and in France’s Pays Basque, where the classic includes potatoes and often chorizo, it’s a regular on tapas counters everywhere. You can eat the frittata straight out of the oven, but part of its appeal is that it’s delicious at room temperature, which is how it’s served at wine bars. You can cut it into small cubes, spearable with a toothpick, and it will be perfect for nibbling standing up at a cocktail party. Or you can slice it into wedges, pair it with salad and bring it out with knives and forks at lunch, brunch or supper. Whatever you call it and however you serve it, it’ll draw fans.

Put most simply, a frittata is a jumble of vegetables and/or meat mixed into a bowlful of beaten eggs and cooked until done.

The add-ins are up for grabs. They can be a mix of leftovers, like small pieces of string beans, potatoes, zucchini, cauliflower, cabbage, roasted chicken or shrimp; snips of bacon; small hunks of sausage or ham. If you think they go together in general, then they’ll go together in your frittata.

For my accompanying frittata, I’m using spring onions, greens and the first of the tomatoes from my local farmers market. I don’t add the tomato slices until the frittata is half-done, so they can hold their shape but still flavor the mix. Oh, and I season the frittata with mustard, a nod to the mustard tart that a friend of mine from Dijon taught me to make.

As an easy rule of thumb: Anything you’re going to add to the eggs should be cooked ahead. You do that in part to soften the vegetables, because they won’t really be cooked in the frittata, and in part to rid them of excess liquid, so they won’t waterlog the eggs.

To make a hearty frittata, you need an ovenproof skillet with high sides. My favorite pan for this is my trusty nine-inch cast-iron skillet, but a nonstick pan will do just as well, and, while I like straight sides, sloping sides are fine.

The onions and garlic in the recipe need a quick cook in olive oil before you pile in the greens. I love using kale for this frittata because of its deep flavor, but spinach is delicious, as is chard. When you first toss in the greens, they’re so voluminous, they threaten to spill over the sides of the skillet. Worry not. Crank up the heat and stir without stop; within a minute, the heat and oil will have wilted the greens, and you’ll be able to mix them neatly in the pan. Taste as you go. You’re cooking the greens mostly for texture, so when they’re just the way you enjoy them, call it quits.

Wipe out the pan: This is a fussy step that shouldn’t be skipped. A clean pan means an easy lift-out when the frittata’s ready to be flipped out for serving.

As for cooking the frittata: It’s easy — so much easier than any kind of omelet. Pour in lightly whisked eggs and don’t do a thing for about two minutes. Then, run a spatula around the edges, gently nudging the eggs inward toward the center of the pan and just slightly upward, so the uncooked portions can slip into newly vacated real estate. Do that one or two times more, and then it’s hands off. Let the eggs go for a few more minutes, until they’re half-cooked — precision isn’t crucial here — then top the frittata with the tomatoes and some cheese and slide the pan into a hot oven to bake until the eggs are set and the frittata is beautifully puffed.

Done. Really. It’s all over except the decision-making: Have it hot? Room temp? Cold? Pack it for picnic? Break out the rosé? Hoard it for late-night snacking? Put out the word that there’s a party at your place? Told you. A frittata’s a dish with possibilities.

Greenspan is the award-winning author of 11 cookbooks, the most recent of which is “Baking Chez Moi.” Read more on her Web site, doriegreenspan.com, and follow her on Twitter: @doriegreenspan. She will host her Just Ask Dorie chat from 1 to 2 p.m. Wednesday: live.washingtonpost.com.