Preheat and Prep: Preheat oven to 375°F (190°C). Grease a 9×13-inch glass baking dish.
Make the Filling: In a large mixing bowl, combine the cream of chicken soup, sour cream, milk, garlic powder, onion powder, salt, and pepper. Mix well. Add the cooked chicken and 1 cup of shredded cheddar cheese. Stir until combined.
Prepare the Biscuits: Cut the refrigerated biscuits into quarters. Gently fold the biscuit pieces into the chicken mixture until they are coated.
Assemble the Casserole: Pour the mixture into the prepared baking dish, spreading it evenly. Sprinkle the remaining 1/2 cup of cheddar cheese on top.
Bake: Bake in the preheated oven for 30–35 minutes, or until the biscuits are puffed and golden brown, and the cheese is melted and bubbly.
Brush with Butter: Remove the casserole from the oven and brush the tops of the biscuits with melted butter for a glossy finish.
Serve: Let the casserole cool for a few minutes before serving. Garnish with fresh parsley or chives if desired.