01 - In a large mixing bowl, combine buttermilk, hot sauce, kosher salt, and black pepper. Submerge chicken thighs in the mixture and marinate for a minimum of 20 minutes or up to overnight under refrigeration.
02 - In a shallow dish, whisk together all-purpose flour, cornstarch, paprika, garlic powder, onion powder, cayenne pepper, and salt until fully combined.
03 - Remove each chicken thigh from the marinade and allow excess liquid to drip away. Coat thoroughly in the flour mixture, pressing to ensure adherence. Rest coated chicken on a wire rack for 10 minutes to promote crust formation.
04 - Pour vegetable oil into a heavy skillet or Dutch oven to a depth of about 1 inch. Heat oil to 350°F (175°C), monitoring with a thermometer for accuracy.
05 - Working in batches, lay chicken thighs carefully into the hot oil. Fry 5 to 7 minutes per side until golden brown and crisp, making sure the internal temperature reaches 165°F (74°C). Transfer to a clean wire rack.
06 - In a mixing bowl, combine half a cup of the hot frying oil with cayenne pepper, brown sugar, chili powder, smoked paprika, garlic powder, and salt. Whisk until smooth and brush liberally over both sides of the fried chicken.
07 - If desired, spread unsalted butter on the cut sides of brioche buns and toast in a skillet until golden brown.
08 - Place each set of sauced chicken thighs on the bottom half of a toasted bun. Top with dill pickle chips and a generous portion of coleslaw. Cap with the top bun and serve promptly.