Thaw and drain spinach, pressing out as much liquid as you can.Spread spinach into a greased or sprayed pie pan.Drain mushrooms and spread over spinach.Break cheese into pieces and lay out evenly over mushrooms.Whisk eggs together with heavy cream and water. Mix in parmesan, garlic powder, salt, and pepper.Pour egg mixture over other ingredients in pie pan.Sprinkle top with mozzarella cheese.Bake at 350°F for 40-55 minutes or until center is set and top is golden brown.