Make the crust by combining the flour, butter, and 1 egg, then pre-bake it for 10 minutes in a 9 inch (22cm) pie tin.
In the meantime, cook the bacon, transfer onto a chopping board and once cooled chop into pieces.
To the same pan, add the spinach and mushrooms, and cook for 5 minutes, until softened. Beat together the eggs and milk, and season with salt, pepper, to taste. Next, add in the chopped bacon, spinach and mushrooms.
Reduce the oven heat to 350°F (170°C) and pour egg mixture into the pre-baked crust. Bake for 40-50 minutes, until cooked through.
To freeze:Cool completely and cover with plastic wrap, and then aluminum foil. Freeze for up to 3 months.
To reheat:Thaw completely. Heat oven to a 350°F (170°C) and bake for 30 minutes, until heated through.