Creamy Chicken Manicotti

This is a family favorite, but I don't make it too often, coz it's not the best for you lol! This was something my mom used to make when I was a teen, and it has always been a favorite of mine. It has manicotti in the title, but we have always used jumbo shells. Much easier than stuffing manicotti.

About 15 jumbo pasta shells
1/2 cup sour cream (I use reduced fat)
1 can (10 3/4 oz.) creamy chicken mushroom soup, undiluted
2 cups chopped cooked chicken (I bake 2 chicken breasts, and dice them, small pieces, when they've cooled)
1/4 cup chopped onion
2 tbsp butter or margarine (I use light stick butter)
1 can (4 oz) sliced mushrooms, DO NOT DRAIN!
1 cup (4 oz) shredded sharp cheddar (can use reduced fat, but it doesn't melt quite as well)

Cook shells according to package directions, omitting salt; drain and set aside. In the meantime, combine the soup and sour cream; mix well. Put half the soup mixture in a separate bowl, and add in the cooked chopped chicken; mix well. Set aside remaining soup mixture. Stuff shells with the chicken mixture; place in a greased 13x9 baking dish. Melt butter in large skillet, add onion and saute' until tender but not browned. Add mushrooms WITH the juices in the can. Stir in the reserved soup mixture and mix well. Spoon over the stuffed shells. Bake uncovered at 350 for 15 minutes. Sprinkle with cheese and bake another 5 minutes or til cheese is melted.
I like to serve with warm buttered bread to soak up all the sauce!