Unforgettable Chicken Casserole

3 cups chopped, deli-roasted chicken
2 cups finely chopped celery
1 cup grated cheddar cheese
1/2 cup slivered almonds
1/2 cup light sour cream
1/2 cup light mayo
1 can cream of chicken soup
1 can water sliced chestnuts
1 1/2 cups french fried onion rings

Stir together everything, except for the french fried onion rings. Spoon into an 11x7 greased baking dish. Bake at 350 degrees for 40 minutes.
Sprinkle onion rings over the top and bake for 5 more minutes.
Let stand 10 minutes before serving.

(I usually double this recipe for my family.)