Preheat your oven to 350°F (175°C) and lightly grease a 9x13 inch baking dish.

In a large mixing bowl, combine shredded cooked chicken, cream of chicken soup, sour cream, garlic powder, onion powder, salt, and black pepper. Stir until well mixed.

Pour the chicken mixture into the prepared baking dish and spread evenly.

In a small bowl, mix crushed buttery crackers with melted butter and poppy seeds until coated.

Sprinkle the topping evenly over the chicken mixture in the baking dish.

Bake uncovered for 25 to 30 minutes until the topping is golden brown and the casserole is bubbling.

Let the casserole cool for about 5 minutes before serving.