Preheat oven to 350º F.
Sprinkle flour on one side of a prepared pie crust. Place in a 9-inch pie plate, floured side down. Flute the edges and prick the bottom. Bake for 10 minutes at 350º F. Set aside and increase oven temperature to 400º F.
Melt butter in a saucepan. Add onions and sauté until nicely browned, 10 to 15 minutes. Add flour, salt, pepper and nutmeg; stir well. Pour into prepared pie crust. Sprinkle Swiss cheese over onion mixture.
Beat eggs until light and fluffy. Add half and half, and milk; whisk to blend well. Pour over onion mixture. Bake at 400º F for 25 minutes or until lightly browned and puffy. Serve immediately. Yield: 6 servings.