Warm through tenders in the oven, approximately 10 minutes. Chop roughly, set aside.
Preheat over to 350.
Cook pasta in boiling water for 7 minutes.
While pasta is cooking, melt 1½ tablespoons of butter in a small skillet. Add diced celery and onion and cook 5 minutes, or until translucent.
Meanwhile, melt 1 tablespoon of butter in a medium saucepan. Whisk in flour and dry mustard; cook 1 minute. Add half-and-half, whisking constantly, until bubbles and thickens, about 2-3 minutes.
When sauce has thickened, add chicken and garlic to the celery and onion. Stir and let cook for 2 minutes.
In batches, add the shredded and cubed cheese to the half-and-half sauce. Stir occasionally until all the cheese has melted. You may need to add a pinch of salt.
Spray a 9x9" baking dish with cooking spray. Layer ½ of the pasta, then top with the chicken mixture. Finish with the remaining pasta, and pour the cheese sauce over the entire dish.
Melt 1 tablespoon of butter in a microwave-safe dish; stir in the panko breadcrumbs.
Spread across the top of the mac & cheese, then sprinkle on parsley.
Bake for 30 minutes, until cheese is bubbly and lightly browned.
Recipe by Views From the Ville at http://viewsfromtheville.com/2013/09/27/tailgating-recipes-buffalo-chicken/