Prepare Dough: In a food processor, pulse flour and salt. Add butter and pulse until mixture resembles coarse crumbs. Gradually add ice water, pulsing until the dough starts to come together. Wrap in plastic and refrigerate for at least 1 hour.

Roll Out: On a floured surface, roll the dough into a 12-inch circle. Place it in a 9-inch pie dish, trim and crimp the edges. Refrigerate while preparing the filling.

Preheat Oven: Preheat your oven to 375°F (190°C).

Cook Bacon: In a skillet, cook the bacon until crispy. Drain on paper towels, then crumble. Scatter the bacon evenly over the bottom of the pie crust.

Add Cheese: Sprinkle the shredded cheese over the bacon.

Combine Eggs and Cream: In a bowl, whisk together eggs, heavy cream, salt, pepper, and nutmeg (if using). If using onion, sauté it until soft and translucent, then add it to the mixture.

Assemble Quiche: Pour the egg mixture into the pie crust, over the bacon and cheese.

Bake: Bake in the preheated oven for 35-45 minutes, or until the quiche is set and the crust is golden brown. To test for doneness, insert a knife near the center—if it comes out clean, the quiche is done.

Cool and Serve: Let the quiche cool for at least 10 minutes before slicing. Serve warm or at room temperature.