Mustard Green and Sweet Onion Frittata

Here's another recipe in the parade of hors d'ouerves I've been testing. It's easy enough and can be made a day or two ahead. It reminds me of the traditional Spanish tapa tortilla espagnola. So I added a little garlic pepper to mayonnaise to serve alongside, much as a traditional Andalucian taverna might serve some aioli alongside your tortilla and cold copita of sherry. The frittata can be served warm, at room temperature or cold.

(Note: I substituted collard greens since my grocery store was out of mustard greens. They still add plenty of a nice bite--and actually I wonder if the mustard greens would make the finished product overly bitter. But whatever greens you use, make sure you chop them fairly finely if you're planning to serve this in canape-size bites. Otherwise, you end up with lots of bits hanging out...not the most attractive presentation.)

Mustard Green and Sweet Onion Frittata
From Food & Wine magazine.

3 tablespoons extra-virgin olive oil
1 large sweet onion, diced
1 1/2 pounds mustard greens (or other greens), stems discarded and leaves fairly finely chopped 16 large eggs, beaten
Kosher salt and freshly ground pepper
1/3 cup grated Parmigiano-Reggiano

Preheat the oven to 350°. In a large ovenproof nonstick skillet, heat 1 tablespoon of the oil. Add the onion and cook over moderately high heat until golden brown, 10 minutes. Add the greens and cook until wilted.

Season the eggs with salt and pepper and whisk in the remaining 2 tablespoons of oil. Pour the eggs into the skillet and cook over moderate heat until the bottom and sides begin to set. Lift the sides of the frittata to allow the uncooked eggs to seep under. Continue cooking until the bottom is set and the top is still runny, 3 minutes. Sprinkle the Parmigiano-Reggiano on top.

Transfer the skillet to the oven and bake for about 8 minutes, until the center of the frittata is set. Slide the frittata onto a cutting board. Cut into 1 1/2-inch squares and serve hot, warm or at room temperature.