Poppy Seed Chicken Casserole

1 tablespoon margarine

8 ounces sliced mushrooms

5 cups cooked chicken -- cubed

1 cream of chicken soup, condensed

1 cup sour cream

2 ounces pimientos -- drain

1/2 cup margarine -- melted

1 1/3 cups crackers -- crushed

2 teaspoons poppy seeds

In a skillet, melt margarine. Saute mushrooms until tender. Stir in chicken, soup, sour cream and pimiento; mix well. Spoon mixture into a greased 2-quart casserole. In a small bowl combine topping ingredients (1/2 cup margarine, the crushed crackers and 2 teaspoons poppy seed). Sprinkle over the chicken. Bake at 350 degrees for 20 minutes.