01 - In a large bowl, mix buttermilk, hot sauce, kosher salt, and black pepper. Add chicken thighs and ensure each piece is fully coated. Refrigerate for at least 20 minutes or up to overnight.
02 - In a shallow dish, combine all-purpose flour, cornstarch, paprika, garlic powder, onion powder, cayenne pepper, and salt. Whisk thoroughly to blend.
03 - Lift chicken from the marinade, allowing excess to drain. Coat each thigh in the flour mixture, pressing firmly so the coating adheres. Place on a wire rack and let rest for 10 minutes.
04 - Pour vegetable oil into a heavy skillet or Dutch oven to a depth of 1 inch. Heat oil over medium-high until it reaches 350°F.
05 - Working in batches, fry the chicken thighs for 5 to 7 minutes per side, until deeply golden and internal temperature reaches 165°F. Transfer cooked chicken to a clean wire rack to drain.
06 - In a bowl, blend 1/2 cup hot frying oil with cayenne pepper, brown sugar, chili powder, smoked paprika, garlic powder, and salt until smooth. Brush sauce liberally over both sides of fried chicken.
07 - (Optional) Spread unsalted butter on cut sides of brioche buns. Toast in a skillet until golden brown.
08 - Place a piece of sauced chicken on each bun base. Top with dill pickle chips and a generous scoop of coleslaw. Cap with the top bun and serve immediately.