Cheesy Frittata with Spinach, Asparagus and Mushrooms

Preheat oven to 325.In a 10-inch ovenproof skillet over medium heat, saute the leek in butter and olive oil until soft.Increase the heat to medium-high and add the asparagus and mushrooms.Saute for 3 minutes.Meanwhile, boil some water and wilt the spinach leaves.Wring dry, being sure to get rid of the excess moisture.Chop the leaves, and add the spinach to the rest of the vegetables and sprinkle with a bit of salt and pepper.In a large bowl, whisk eggs, egg whites, 1 cup Fontina cheese, 1/8 cup Parmesan, seasonings, and the fresh herbs.Add to saute pan, sprinkle with remaining cheeses, and bake for about 35 minutes until edges are golden brown and eggs are set.