Stuffed Shells

1 box lg. jumbo shells
3/4 lb. hamburger
1/4 c. chopped onion
3 oz. cream cheese
1 c. shredded mozzarella
1 c. shredded cheddar cheese
1/2 c. sour cream
1 jar spaghetti sauce
3/4 c. Parmesan cheese

Brown hamburger and onion. Boil shells according to directions on package. Add cream cheese, sour cream, mozzarella and cheddar cheese to cooked meat, until it combines and softens. Stuff shells with mixture. In bottom of 9 X 13-inch pan pour a little spaghetti sauce in pan, just enough to cover, set shells on top and then pour remaining sauce over the shells. Sprinkle over the Parmesan. Bake at 350 for 30-40 minutes.