Chicken and Spinach Stuffed Shells

I'm not even sure where I got this recipe, so I'm sorry I can't give credit where credit is due.  I'll tell ya what, though, they deserve it!!  This is so good!!  It's a lot of work, but it's worth it.

44 uncooked jumbo pasta shells (about 1 1/2 12-oz boxes)--I've used Manicotti noodles before, and it's actually faster...
2 c chopped cooked chicken
2 c fresh chopped spinach
1 onion, minced
2 cloves garlic, minced
1 (15 oz) container ricotta cheese
2 (8 oz) packages cream cheese, softened
1 (5 oz) package shredded Parmesan cheese
1 large egg, lightly beaten
1 Tbsp dried parsley flakes
1 tsp Italian seasoning
1/2 tsp salt
1/2 tsp pepper
2 c shredded mozzarella cheese, divided
1 (26 oz) jar prepared spaghetti sauce (any variety)

Cook shells according to package directions; drain and set aside.
Preheat oven to 350 degrees.  Lightly grease 2-13X9X2 inch baking dishes.
In a large bowl, combine chicken and all the rest of the ingredients except mozzarella and spaghetti sauce.  Stir in 1 cup mozzarella.  Spoon into shells.  Spread half of the spaghetti sauce into prepared baking dishes.  Arrange shells over sauce; top with remaining sauce.  Cover tightly with aluminum foil.  Bake, covered for 40 minutes.  Uncover and sprinkle with remaining 1 cup mozzarella.  Bake for 5-10 more minutes.

Makes 8-10 servings.