Let’s get cooking! Here’s how to bring this quiche to life, step by step.

1. Preheat your oven to 375°F (190°C). Place the pie crust in a 9-inch pie pan and crimp the edges for a decorative look.
2. In a skillet over medium heat, cook the bacon until crispy. Transfer to a paper towel-lined plate to drain, then crumble into pieces.
3. In the same skillet, melt the butter and add the sliced onions. Cook slowly over medium-low heat, stirring occasionally, until the onions are golden brown and caramelized, about 25 minutes.
4. Spread the caramelized onions evenly over the bottom of the pie crust. Sprinkle the crumbled bacon and shredded Gruyère cheese on top.
5. In a mixing bowl, whisk together the eggs, heavy cream, milk, salt, pepper, and nutmeg until smooth.
6. Pour the egg mixture over the onions, bacon, and cheese in the pie crust.
7. Bake in the preheated oven for 35-40 minutes, or until the quiche is set and slightly golden on top. A little jiggle in the center is fine; it will firm up as it cools.
8. Allow the quiche to cool for about 10 minutes before slicing. This will help it set and make serving easier.