More-Vegetable-Than-Egg Frittata

Preparation

1. Step 1

   Put olive oil in a skillet (preferably nonstick or well-seasoned cast iron) and turn heat to medium. When fat is hot, add onion, if using, and cook, sprinkling with salt and pepper, until it is soft, 3 to 5 minutes. Add vegetables, raise heat and cook, stirring occasionally, until they soften, from a couple of minutes for greens to 15 minutes for sliced potatoes. Adjust heat so vegetables brown a little without scorching. (With precooked vegetables, just add them to onions and stir before proceeding.)

2. Step 2

   When vegetables are nearly done, turn heat to low and add herb. Cook, stirring occasionally, until vegetables are tender.

3. Step 3

   Meanwhile, beat eggs with some salt and pepper, along with cheese if you are using it. Pour over vegetables, distributing them evenly. Cook, undisturbed, until eggs are barely set, 10 minutes or so; run pan under broiler for a minute or two if top does not set. Cut into wedges and serve hot, warm or at room temperature.