Preheat oven to 400°. Lightly prick bottom of pie shells all over and then bake for 5 minutes. Remove and cool while preparing the filling. Reduce heat to 350°.

In large skillet, cook the sausage for about 5 minutes over medium heat, stirring often. Add the onion, garlic and mushrooms and cook another 5 minutes. Add spinach, cook 1 minute. Remove to bowl and cool for 10 minutes.

In a large bowl, beat eggs and then stir in the 3 cheeses, cream, flour and pepper. Combine the egg mixture with the sausage mixture and divide between the 2 pie shells. Bake for 30 minutes, or until center is set. Let stand for about 5 minutes before serving.