At least an hour before starting to cook, remove the pie crust from the fridge so that it warms up to room temperature.
Pre-heat oven to 375 °F.
Remove the sausages from their casings. Over medium heat, cook sausage meat until well-browned, about 10 minutes. Remove to a bowl with a slotted spoon.
In the sausage fat, cook the mushrooms over medium heat until tender. Remove with a slotted spoon and store with the browned sausage meat.
Mix the eggs, sausage, mushrooms, spinach, mozzarella, ricotta, salt, pepper, and garlic powder.
Roll out a little more than half the pie dough, and place in the bottom of the pie plate.
Spoon the mixture into the pie.
Roll out the rest of the pie dough, and place it over the pie. Cut slits in the top to let the steam escape.
Bake in oven at 375 °F for 1 hour, or until a knife inserted in the centre comes out clean.
