In a large mixing bowl, combine the cream of mushroom soup, sour cream, chicken broth, garlic powder, salt, and pepper. Stir until smooth.
Add the cooked chicken, mushrooms, and 1/2 of the cheese to the mixture. Stir to combine.
Transfer the mixture into a greased 9x9-inch casserole dish.
Top with remaining cheese and breadcrumbs if desired.
Bake for 30-35 minutes or until bubbly and golden brown on top.
Notes
You can substitute the chicken for turkey or even a plant-based protein for variety. For a dairy-free version, use a non-dairy cream soup and cheese alternative.