01 - Preheat oven to 375°F. Lightly grease a 9x13-inch casserole dish with cooking spray or butter.
02 - In a large skillet over medium heat, sauté the diced onion, celery, and sliced jalapeños in a small amount of oil until softened, about 4 to 5 minutes. Stir in the minced garlic and cook for 1 additional minute until fragrant.
03 - In a large mixing bowl, combine the softened cream cheese, sour cream, Buffalo wing sauce, salt, black pepper, and smoked paprika. Stir until smooth and well blended.
04 - Fold the shredded chicken and sautéed vegetables into the creamy base. Add half of the cheddar cheese and half of the mozzarella cheese, then mix thoroughly to distribute evenly.
05 - Transfer the mixture into the prepared casserole dish, spreading it into an even layer. Sprinkle the remaining cheddar and mozzarella cheeses evenly across the top.
06 - Bake uncovered for 25 to 30 minutes, until the cheese is bubbly and golden brown on top.
07 - Remove from the oven and scatter blue cheese crumbles and sliced green onions over the top, if desired.
08 - Let the casserole rest for 5 minutes before serving to allow the filling to set.