Preheat oven to 350°F and grease a 9x13-inch baking dish.
If using fresh broccoli, steam for 3-4 minutes until bright green and slightly tender. Drain well.
In a large bowl, combine cream of chicken soup, sour cream, milk, garlic powder, 1 cup of shredded cheese, salt, and pepper. Mix until smooth.
Fold in the cooked chicken, broccoli, and rice until everything is well coated.
Pour the mixture into the prepared baking dish and spread evenly. Top with remaining 1 cup of cheese.
Mix crushed Ritz crackers with melted butter and sprinkle over the top of the casserole.
Bake uncovered for 30-35 minutes until bubbly and golden on top. Let rest 5 minutes before serving.