Preheat your oven to 350°F (175°C). Lightly grease a 9x13-inch baking dish with cooking spray or a little butter.
In a large mixing bowl, combine the sour cream, cream of chicken soup, garlic powder, onion powder, and black pepper. Stir until smooth. Fold in your shredded chicken until every piece is fully coated.
Spread the creamy chicken mixture into an even layer in the bottom of your prepared baking dish. Use a spatula to smooth out the top.
Place the Ritz crackers into a large zip-top bag and gently crush them with your hands or a rolling pin until you have coarse crumbs (you don't want powder, you want texture). In a medium bowl, toss the crushed crackers with the melted butter and the poppy seeds until all the crumbs are evenly moistened.
Sprinkle the buttery cracker mixture evenly over the top of the chicken layer, covering it completely from edge to edge.
Bake uncovered for 25 to 30 minutes. You'll know it's done when the creamy sauce is bubbling up around the edges and the cracker crust has turned a golden brown. Let it cool for 5 minutes before scooping.
