Jamie's Spinach Manicotti

1 box manicotti shells, cooked
1 140z. jar ricotta cheese
3 c. spaghetti sauce
2 cups mozzarella cheese
1/2 c. parmesan cheese
1 egg
1 (10 oz.) pkg spinach, chopped

Mix together all cheeses, egg and spinach. Stuff into cooked manicotti and put in 13 x 9 dish. Pour sauce over noodles. Cover with foil and cook at 350 degrees for 35-40 minutes. Remove cover and add extra mozz. cheese if desired.