Spinach-Mushroom Quiche

Preheat the oven to 400 degrees F. Saute mushrooms and onion in butter in a large skillet for 10 minutes or until soft; set aside to cool. Sprinkle the bottom of pie shell with Swiss cheese. In a large bowl, lightly beat the eggs, then add milk, spinach, mushrooms and onion, salt, pepper, and nutmeg; stir well. Gently pour the egg mixture over the Swiss cheese in the pie shell and sprinkle Parmesan cheese on top. Bake at 400 degrees F for 10 minutes, then reduce heat to 350 degrees and continue baking for another 30 to 40 minutes, or until knife inserted in center comes out clean. Allow it to stand for 15 to 20 minutes before cutting. Serve slightly warm.