Preheat oven to 375°F (190°C)
Thaw and drain frozen spinach (if using) and squeeze dry
In a bowl, whisk eggs with salt, pepper, and any herbs/spices
Stir in milk or cream
Add cheese and any fillings (e.g., cooked bacon/sausage, sautéed vegetables, spinach)
Roll out pie crust and fit into a 9-inch (23 cm) pie dish
Trim edges and optionally crimp
If using raw fillings, spread them evenly in the crust
Pour egg mixture over fillings
Sprinkle extra cheese on top (optional)
Bake 35–50 minutes, until the center is set and the top is lightly browned
Let cool 10–15 minutes before slicing
Serve warm or at room temperature