01 - In a large mixing bowl, whisk together buttermilk, hot sauce, kosher salt, and black pepper. Submerge chicken thighs in marinade, cover, and refrigerate for at least 20 minutes or up to overnight for best flavor.
02 - In a shallow dish, thoroughly blend together all-purpose flour, cornstarch, paprika, garlic powder, onion powder, cayenne pepper, and salt.
03 - Remove chicken pieces from marinade, allowing excess liquid to drain off. Dredge each thigh evenly in the seasoned flour mixture, pressing to adhere. Set coated chicken on a wire rack and rest for 10 minutes.
04 - Pour vegetable oil into a heavy skillet or Dutch oven to a depth of 1 inch. Heat over medium-high heat to 350°F (175°C).
05 - Working in batches, fry chicken thighs for 5 to 7 minutes per side, until golden and crisp. Ensure internal temperature reaches 165°F before removing to a wire rack to drain.
06 - In a bowl, whisk 1/2 cup hot frying oil with cayenne pepper, brown sugar, chili powder, smoked paprika, garlic powder, and salt until smooth. Brush the spicy oil mixture generously over both sides of the fried chicken.
07 - If desired, spread cut sides of brioche buns with unsalted butter and toast in a clean skillet until golden brown.
08 - Place sauced chicken thigh on each bun base. Top with dill pickle chips and a generous scoop of coleslaw. Cap with the top bun and serve immediately.