Preheat the oven to 350°F (175°C).
Cook the rotini pasta according to package instructions until al dente.
In a large mixing bowl, combine shredded chicken, Buffalo sauce, cream cheese, milk, garlic powder, onion powder, salt, and pepper.
Once the pasta is cooked, drain it and immediately add it to the mixing bowl with the other ingredients.
Add 2 cups of shredded cheddar cheese into the mixture and stir until combined.
Transfer the mixture into a greased 9x13-inch baking dish, spreading it evenly.
In a small bowl, combine panko breadcrumbs with melted butter, then sprinkle over the top of the casserole.
Bake uncovered in the preheated oven for 25-30 minutes, or until the top is golden and bubbling.
Once done, remove from the oven and let it sit for 5-10 minutes before serving.