Preheat oven to 325°F (160°C).

Prepare pastry for a single crust pie.

Cook bacon until crisp and crumble.

Reserve bacon drippings and cook sliced onion in it until tender.

In a large bowl, mix eggs, milk, cream, flour, salt, and nutmeg.

Stir in the crumbled bacon, cooked onion, and shredded Swiss cheese.

Pour the mixture into the prepared pastry shell.

Cover the edges of the crust with foil to prevent overbrowning, if needed.

Bake for 45 to 50 minutes, or until a knife inserted into the center comes out clean.

Let cool slightly before serving.