1 (7 oz.) box spaghetti
1 (32 oz.) jar spaghetti sauce
1 egg
1/2 c. milk
1 lb. hamburger
2 c. Mozzarella cheese, shredded
2 c. cheddar cheese, shredded
1/4 c. onion, chopped

Lay 1 (17 oz.) box spaghetti, cooked and drained, in a 9"x13" ungreased pan. Mix egg and milk; pour over spaghetti. Brown one pound of hamburger and onion. Pour over spaghetti. Add spaghetti sauce over the top. Sprinkle on the cheese. Mushrooms are optional. Bake at 350 degrees for 40 to 45 minutes, uncovered. Let stand 5 minutes before serving.