1. Chop the white and pale green parts of the leeks (you'll only use those), thinly slice the mushrooms, coarsely chop the parsley.

2. Place a rack in upper third of oven; preheat to 350°. Heat 1 tablespoon oil per 6 servings in a nonstick ovenproof something over medium heat. Add leeks; cook, stirring often, until softened, about 5 minutes. Add mushrooms and cook, stirring often, until softened and all liquid has evaporated, 8-10 minutes.

3. Meanwhile, whisk eggs and parsley in a large bowl. Season with salt and pepper.

4. Increase the heat to medium-high and add remaining 1 tablespoon oil to the skillet. Pour the egg mixture over the mushrooms, shaking the pan to evenly distribute mixture. Cook the frittata, without stirring, until its edges begin to set, about 5 minutes.

5. transfer skillet to oven. Bake frittata until golden brown and center is set, 25-30 minutes.

P.S. If you can't find an ovenproof skillet, just transfer everything to a pan that can go in the oven before putting it in.