Spinach-Mushroom Lasagna

1 (15-oz.) carton ricotta cheese 

1 egg, beaten 

2 c. shredded mozzarella cheese, divided 

1 (28-oz.) jar spaghetti sauce 

8 oz. lasagna noodles (uncooked) 

2 bunches fresh spinach (about 1 1/2 lbs.), washed and stemmed 

2 c. sliced fresh mushrooms whole mushrooms (optional) 

Combine ricotta cheese, egg, and 1 c. shredded mozzarella in a medium-size bowl; set aside. Pour half the spaghetti sauce in the bottom of lightly greased 9x13-inch baking dish. Cover the sauce with half the noodles. Spread the cheese-egg mixture over the noodles, followed by the spinach, mushrooms, remaining mozzarella cheese, remaining noodles, and remaining sauce. Pour 2 T. water into each corner of the dish. Cover dish securely with aluminum foil, and bake at 350 degrees for 1 1/4 hours. Do not unseal until cooking time is complete. Remove from the oven, uncover carefully, and let stand for 10 to 15 minutes before serving. Garnish with whole mushrooms, if desired. Note: One (10-oz.) package of frozen chopped spinach, thawed and drained, may be substituted for the fresh spinach.