01 - Preheat oven to 350°F. Lightly grease a 9x13-inch baking dish.
02 - Boil the pasta in salted water until al dente. Drain well and set aside.
03 - In a large mixing bowl, whisk together buffalo sauce, softened cream cheese, sour cream, whole milk, garlic powder, onion powder, smoked paprika, salt, and pepper until the mixture is smooth and homogeneous.
04 - Add shredded or cubed chicken breast and drained pasta to the sauce, stirring to coat evenly.
05 - Fold in half of the mozzarella cheese and all of the shredded cheddar until evenly distributed.
06 - Transfer mixture to the prepared baking dish and spread into an even layer.
07 - Sprinkle remaining mozzarella cheese and blue cheese (if using) over the surface.
08 - Bake uncovered for 25–30 minutes, until the casserole bubbles and the cheese on top is golden.
09 - Remove from oven and rest for 5 minutes. Garnish with sliced green onions and parsley before serving.