In a 2 guart casserole, melt the butter. Add 1 tube of crushed crackers to make a crust. In a medium sized bowl, mix together the chicken, soup, sour cream, 1/4 tube crushed crackers, and the poppy seeds. Add any personal favorite seasonings such as salt, pepper, garlic, and so on if desired. Pour into the casserole over the crust. Bake in a 350 degree oven until hot and bubbly.