Preheat the oven to 350°F (175°C).
In a large mixing bowl, combine the diced chicken, chopped spinach, cream of chicken soup, sour cream, garlic powder, onion powder, salt, and pepper.
If adding rice or pasta, fold it into the mixture at this point.
Pour the mixture into a greased baking dish and spread evenly.
Top with shredded cheddar cheese.
Cover with aluminum foil and bake for 25 minutes.
Remove the foil and bake for an additional 10-15 minutes until cheese is melted and bubbly.
Allow to cool for a few minutes before serving.