Prepare the crust (15 minutes + chilling)
Roll out pie dough into a 9-inch tart pan or pie dish.
Line with parchment paper, fill with pie weights or dried beans, and blind bake at 375°F (190°C) for 15 minutes.
Remove weights and parchment, then bake another 10 minutes until lightly golden.
Cook the bacon and onion (10 minutes)
In a skillet over medium heat, cook chopped bacon until crisp. Remove and drain on paper towels.
In the bacon drippings, sauté onion until soft and translucent.
Make the custard filling (5 minutes)
In a large bowl, whisk the eggs, cream, and milk until smooth.
Season with salt, pepper, and nutmeg.
Assemble the quiche (5 minutes)
Spread bacon and onions evenly over the baked crust.
Sprinkle shredded Gruyère on top.
Pour custard mixture over the filling.
Bake the quiche (35–40 minutes)
Bake at 375°F (190°C) until the filling is just set and the top is lightly golden.
A knife inserted in the center should come out mostly clean, with just a slight jiggle.
Cool and serve (10 minutes)
Let quiche rest for at least 10 minutes before slicing. Serve warm or at room temperature.