Poppy Seed Chicken Casserole

4 boneless, skinned chicken breasts, cooked until tender
2 cans cream of chicken soup (undiluted)
1/2 cup sour cream
36 Ritz crackers rolled into crumbs
1 Tbsp. poppy seeds

TOPPING
36 Ritz crackers, rolled into crumbs
2 tsp. poppy seeds
1 stick margarine or butter, melted

Cut cooked chicken into small pieces (I shred it with my fingers). Add the next 4 ingredients to the chicken and place in a 9x13-inch baking dish. Sprinkle cracker crumbs over the top, then sprinkle on the poppy seeds. Drizzle melted margarine over casserole. Bake in a 325-degree oven for 30 minutes.