Wild Rice and Chicken Casserole

2 (6.2 oz) packages fast cooking long grain rice mix (Uncle Ben's)
1/4 cup butter or margarine
4 celery ribs, chopped
2 med onions, chopped finely
5 cups cooked chicken, chopped
4 cups (1 lb) shredded medium sharp cheddar cheese
2 cans cream of mushroom soup
1 (16 oz) carton of sour cream
1 cup milk
1/2 tsp salt
1/2 tsp pepper
1 (2 1/4 oz) oz package sliced almonds

Prepare the rice mixes according to directions on package. Sauté celery and onion in melted butter in large skillet over medium heat until tender (about 10 min). Stir celery, onion, chicken, soup, sour cream, milk, salt, pepper, and 3 cups of cheese (reserving one cup). Spoon mixture unto a 4 quart baking dish or divide into 2 or 3 smaller baking dishes. Bake 350 degrees for 35 minutes. Sprinkle with remaining cheese and almonds, bake for 5 more minutes. 

Note: This casserole feeds at least 12 people. It can easily be halved. Freezes well.