Prepare the Oven: Preheat your oven to 350°F (175°C). Grease a 9×13-inch baking dish with cooking spray or butter.
Combine the Ingredients: In a large mixing bowl, combine the cooked rice, cooked chicken, steamed broccoli, cream of chicken soup, sour cream, mayonnaise, garlic powder, onion powder, paprika, salt, and black pepper. Mix until well combined. Fold in 1 1/2 cups of the shredded cheddar cheese.
Assemble the Casserole: Spread the mixture evenly into the prepared baking dish. Sprinkle the remaining 1/2 cup of shredded cheddar cheese over the top.
Add the Topping (Optional): In a small bowl, mix the crushed Ritz crackers or breadcrumbs with the melted butter. Sprinkle the mixture over the top of the casserole for a crispy topping.
Bake: Place the casserole in the preheated oven and bake for 25-30 minutes, or until the cheese is melted and bubbly and the top is golden brown.
Serve: Let the casserole cool for 5-10 minutes before serving. Enjoy the comforting flavors of this cheesy, hearty dish!