01 - Combine buttermilk, hot sauce, kosher salt, and black pepper in a large mixing bowl. Submerge chicken thighs in the mixture and refrigerate for at least 20 minutes or up to overnight.
02 - In a shallow dredging dish, whisk together all-purpose flour, cornstarch, paprika, garlic powder, onion powder, cayenne pepper, and salt until thoroughly blended.
03 - Remove chicken from marinade, allowing excess to drip off. Coat each thigh in the seasoned flour mixture, pressing firmly to ensure adhesion. Arrange on a wire rack and rest for 10 minutes.
04 - Pour vegetable oil into a heavy skillet to a depth of 1 inch. Heat the oil over medium-high until it reaches 350°F.
05 - Working in batches, fry chicken thighs for 5 to 7 minutes per side, or until golden brown, crisp, and internal temperature reaches 165°F. Transfer to a clean wire rack to drain.
06 - In a medium bowl, whisk together 1/2 cup hot frying oil, cayenne pepper, brown sugar, chili powder, smoked paprika, garlic powder, and salt until a smooth sauce forms. Generously brush both sides of fried chicken with the sauce.
07 - Butter the cut sides of each brioche bun and toast in a skillet over medium heat until golden and crisp.
08 - Arrange sauced chicken thighs on the bottom halves of the toasted buns. Top with dill pickle chips, a generous scoop of coleslaw, and finish with the top bun. Serve immediately for best texture and flavor.