Cook the bacon over medium-low heat until crisp. Place on a paper-towel lined plate to cool then crumble.
In the pan you used to cook the bacon, pour off all but 2 tablespoons of the bacon grease. Add the onion and cook over medium-high heat until softened, about 6-8 minutes. Let the onion cool.
In a medium bowl, whisk together the eggs, cream, milk, flour, salt and nutmeg until smooth. Stir in the Swiss cheese, bacon and onion.
Preheat the oven to 450F. To help the pie crust keep its shape, press 2 layers of foil into the crust to line it. Bake the crust for 10-12 minutes, until nearly done. This will ensure the quiche crust is crispy on the bottom.
Reduce the oven temperature to 325F. Pour the filling into the hot crust and bake for 45-50 minutes, until the center is set. (I test the middle with a knife or toothpick and make sure it comes out clean.)
Let cool at least 20 minutes before serving. This quiche can also be cooled and served at room temperature. Store in the refrigerator and reheat slices individually for up to 3 days. Enjoy!