Preheat oven to 350°. Stir together Homemade Cream of Mushroom Soup, chicken, sour cream, and poppy seeds. Spoon into a lightly greased 11- x 7-inch baking dish. Stir together melted butter and crushed crackers; sprinkle over casserole. Bake 35 to 40 minutes or until bubbly. Let stand 5 minutes before serving.