In a large bowl, combine shredded chicken, chicken broth, melted butter, cream of chicken soup, sour cream, garlic powder, and black pepper. Mix well.
Add broccoli florets, if using, and stir to combine.
Transfer mixture to a greased 9x13-inch baking dish.
Top with stuffing mix, pressing gently to spread evenly.
Bake for 30 minutes or until golden and bubbly.
Let rest for 5 minutes before serving.
Notes
Store leftovers tightly covered in the refrigerator for up to 3 days. Best frozen before baking; wrap tightly and freeze, then thaw overnight in the refrigerator before baking as directed. Can be assembled up to 24 hours ahead and refrigerated before baking.