
Preheat oven to 400°F. Line a 9-inch pie plate with pie crust.
Prick the crust with a fork and pre-bake with weights for 25 minutes.
Sauté shallots in butter until browned.
Whisk eggs, cream, mustard, salt, and pepper together.
Layer shallots, spinach, and cheese in the crust, then pour egg mixture on top.
Bake for 25-30 minutes until set and lightly browned.
Allow to rest for 10-20 minutes before slicing. Serve warm or at room temperature.