Tip:If the handle of your skillet isn't ovenproof, wrap the handle well with foil.
Heat the oven to 400ºF. Whisk the eggs vigorously with the salt, and pepper. In an ovenproof 10-inch enameled cast-iron or nonstick skillet, heat the butter over medium heat. Add the mushrooms, and sauté until browned and tender. Stir in the asparagus. Turn the heat to medium high and then pour the eggs into the pan. Let the eggs set for several seconds, and then, with a heatproof spatula, gently stir the eggs, starting from the center. This will make the frittata puff up more in the oven. Lift the edges so that the eggs flow to bottom. When the frittata is half-set, sprinkle on the Parmigiano. Transfer the pan to the heated oven. Cook for about 10 minutes, until puffed and golden.
nutrition information (per serving):
with 3 Tbs. olive oil total;
sat fat g