1Heat oven to 400. Spray a lg baking pan w/ cooking spray. Cook shells as directed, drain. Place shells in baking pan. Spray a saucepan w/ cooking spray. Saute onion and garlic over medium heat until tender. Add mushrooms and cooked until browned.
2In lg bowl, combine ricotta cheese, mozzarella cheese, egg, spinach, basil, oregano, pepper and onion mix. Mix well. Spoon mix evenly into shells. Top w/ pasta sauce. Sprinkle w/ parmesan cheese.
3Cover pan w/ foil and bake 35 mins, or until bubbly.