Preheat the oven at 180C (375F).
Place the pie crust on a baking pan and pierce lightly all over with a fork (around 2 inches apart).
Beat the eggs, milk, and heavy cream in a large bowl.
Cook the bacon in a frying pan for a few minutes.
If added mushrooms or onions, lightly sauté those in the frying pan as well.
Add the bacon, cheese, salt, pepper, and any optional ingredients into the egg mixture.
Spread the mixture across the pie crust.
Sprinkle across the top a pinch of nutmeg.
Place in the oven for 45 minutes or until the top crust is browned.
Cover with lid and serve while warm.