Jennie's Favorite Chicken-and-Wild Rice Casserole

from Southern Living 2000 Annual Recipes This freezes really well.
Prep: 30 minutes
Bake: 35 minutes

Ingredients:

2 (6.2-oz.) packages fast-cooking long-grain and wild rice mix
¼ C butter or margarine (I use a little olive oil instead.)
2 medium onions, chopped
4 celery ribs, chopped
2 (8-oz.) cans sliced water chestnuts, drained
5 C chopped cooked chicken (2 whole chickens)
4 C (1 pound) shredded Cheddar cheese, divided
2 (10¾ -oz.) cans cream of mushroom soup, undiluted (I use low-fat.)
2 (8-oz.) containers sour cream (I use non-fat.)
1 C milk (I use skim.)
½ t salt
½ t pepper
½ C soft breadcrumbs (optional)

Directions:

Prepare rice mixes according to package directions; set aside.
Melt butter in a large skillet over medium heat; add onion, celery, and water chestnuts. Sauté 10 minutes or until tender.Stir in rice, chicken, 3 cups cheese, and next 5 ingredients.Spoon mixture into a lightly greased 15- x 10-inch baking dish or a 4-quart casserole. Top casserole with breadcrumbs, if desired.Bake casserole at 350˚ for 30 minutes. Sprinkle with remaining 1 cup cheese; bake 5 more minutes. Yield: 6 to 8 servings.