Combine sriracha and buttermilk. Cut chicken breasts in half lengthwise and add to buttermilk marinade. Let sit in the fridge for an hour to marinade. If desired, it can marinade overnight though only 1 hour is needed.
Once the chicken is fully marinated, preheat oven to 365 degrees. Lightly grease your baking dish of choice - preferably cast iron but any oven safe baking dishes work fine.
Bring a large pot of heavily salted water to a boil. Cook to package instructions for al dente, minus 1 minute. Drain and set aside in a bowl - mix noodles with a bit of cooking oil to prevent from sticking.
Grate the cheese if it isn't already and mix cheeses together. Divide into 3 groups, ½ of it for the sauce and two ¼ groups for the casserole and topping respectively.
Heat a medium saucepan over medium heat. Melt in butter until slightly bubbled but not brown, add in flour and whisk to combine. Cook for about a minute to cook out the flour. Slowly incorporate the milk & half and half while whisking constantly. Allow to thicken enough that it coats the back of a spoon - thicker than cream but less thick than condensed soup. Make sure to whisk constantly to avoid the sauce burning or sticking to the bottom of the pan.
Remove from heat and mix in the remaining spices and the ½ section of cheese. Allow the cheese to melt completely. In a large mixing bowl, combine the cooked pasta, cheese sauce and one of the ¼ portionss of the grated cheese. Place in your oven safe dish and top with the remaining ¼ portion of cheese.
Bake for 15 minutes uncovered until bubbly around the edges. If the top isn't browned to your liking, place the oven on broil. Watch closely to avoid burning the cheese. When cooked to desired crispiness, remove from oven and set aside.
While the mac and cheese is baking, mix together flour, thyme, mustard powder, onion powder, garlic powder, paprika, cayenne, salt and pepper to create a flour dredge coating.
Remove chicken from fridge and shake off excess buttermilk. Coat in flour mixture. Repeat process of buttermilk and flour coating 2 times. Set aside.
Heat oil in a large pot, dutch oven or deep fryer to 360 degrees. The cooking temperature should be 350 degrees, but adding the chicken will lower the temperature.
Cook chicken until browned and cooked internally, about 3 minutes per side (juices should run clear) or a meat thermometer reads 165 degrees for food safety. Set aside on a wire rack to wait for assembly.