Preheat your oven to 350°F (175°C).
In a large mixing bowl, combine the shredded chicken, cooked rice, broccoli, cream of chicken soup, sour cream, chicken broth, garlic powder, onion powder, salt, and pepper. Mix well until all ingredients are evenly incorporated.
Transfer the chicken and rice mixture into a greased 9x13 inch baking dish. Spread it evenly.
Sprinkle 1 cup of shredded cheddar cheese on top of the mixture. If using, add breadcrumbs for extra crunch.
Cover the dish with aluminum foil and bake in the preheated oven for 30 minutes.
After 30 minutes, remove the foil and bake for an additional 15 minutes, or until the cheese is bubbly and golden brown.
Remove the casserole from the oven and let it cool for a few minutes before serving.