Shiitake Mushroom and Cheese Frittata
- 8 ounces shiitake mushrooms, stems discarded, caps cut into 1/4-inch slices
- 1 small onion (about 6 ounces), halved and cut into 1/4-inch-thick slices
- 1 1/2 teaspoons fresh thyme
- 2 tablespoons olive oil
- Coarse salt
- 10 large eggs
- 1/2 cup ricotta cheese
- 1/4 teaspoon freshly ground pepper
Preheat oven to 350 degrees. Heat oil in a 9-or 10-inch ovenproof nonstick skillet over medium heat until hot but not smoking. Add mushrooms, onion, and thyme; cook, stirring, until mushrooms and onion are golden brown, about 10 minutes. Stir in 1/2 teaspoon salt; remove skillet from heat.
Whisk eggs in a large bowl until frothy. Stir in the ricotta, 1 teaspoon salt, and pepper to taste. Place reserved skillet over medium heat. Immediately pour in egg mixture, and lightly stir to distribute mushrooms and onion evenly. Reduce heat to medium-low; cook 2 minutes, drawing cooked egg away from sides with a rubber spatula to let uncooked egg flow underneath. Cook until just starting to set, about 2 minutes more.
Transfer skillet to oven. Bake until frittata is just set and top is pale golden, 10 to 12 minutes. Serve frittata in skillet, or slide onto a serving platter.