Directions

1. Preheat oven to 350°F. Butter a 9x13 baking dish.
2. Bring a large pot of salted water to a boil, add elbow macaroni and cook until al dente, about 7 minutes. Drain.
3. Melt 3 tablespoons butter in a large skillet over medium heat. Add onion and celery; cook until soft, about 5 minutes. Stir in chicken and garlic; cook 2 minutes, then add 1/2 cup hot sauce. Simmer until slightly thickened.
4. Melt 2 tablespoons butter in a medium saucepan over medium heat. Add flour and mustard and whisk until smooth. Whisk in the half and half and milk, then add the remaining 1/4 cup hot sauce. Stir until thickened, about 2 minutes. Whisk in the cheeses, then whisk in the sour cream until smooth.
5. Using a large mixing bowl, thoroughly mix together the macaroni, chicken mixture and sauce. Pour into the buttered baking dish.
6. Put the remaining 2 tablespoons of butter in a microwave safe bowl and microwave until melted. Stir in the breadcrumbs, blue cheese and parsley. Sprinkle on top of the casserole and bake until bubbly, 30 to 40 minutes. Let rest about 10 minutes before serving.