In a large mixing bowl, combine the shredded chicken, chopped spinach, cream cheese, sour cream, and half of the mozzarella cheese. Mix until well combined.
Add the chicken broth to the mixture, followed by the garlic powder, onion powder, red pepper flakes (if using), and season with salt and pepper. Stir until everything is evenly incorporated.
Transfer the chicken-spinach mixture into a greased 9x13 inch baking dish, spreading it evenly.
In a small bowl, mix the breadcrumbs with olive oil until the breadcrumbs are lightly coated. Sprinkle the breadcrumb mixture over the top of the casserole.
Finish by topping the casserole with the remaining mozzarella cheese.
Bake in the preheated oven for 30 minutes, or until the casserole is bubbling and the breadcrumbs are golden brown.
Once done, remove from oven and let it sit for 5-10 minutes before serving.
Notes
Let the casserole sit for a few minutes before serving for better slicing.