01 - In a large mixing bowl, whisk together buttermilk, hot sauce, kosher salt, and black pepper. Submerge chicken thighs in the marinade and refrigerate for at least 20 minutes or overnight for enhanced tenderness.
02 - Combine all-purpose flour, cornstarch, paprika, garlic powder, onion powder, cayenne pepper, and salt in a shallow dish, whisking thoroughly to distribute spices evenly.
03 - Remove chicken thighs from marinade, allowing excess to drip off. Dredge each piece thoroughly in the flour mixture, pressing to form an even coating. Arrange coated chicken on a wire rack and rest for 10 minutes.
04 - Pour vegetable oil into a heavy skillet or Dutch oven until oil reaches a 1-inch depth. Preheat oil to 350°F using a kitchen thermometer for accuracy.
05 - Using tongs, carefully place coated chicken thighs into hot oil. Fry in batches for 5 to 7 minutes per side until crisp, golden brown, and internal temperature registers 165°F. Transfer to a wire rack to drain.
06 - In a heatproof bowl, whisk together 1/2 cup hot frying oil, cayenne pepper, brown sugar, chili powder, smoked paprika, garlic powder, and salt until smooth and homogenous.
07 - Brush Nashville hot sauce generously over both sides of fried chicken using a pastry brush while the chicken is still warm.
08 - Optional: Spread unsalted butter on cut sides of brioche buns. Toast in a skillet over medium heat until golden brown.
09 - For each sandwich, arrange sauced chicken on the lower brioche bun, top with dill pickle chips and a scoop of coleslaw. Cap with upper bun and serve immediately.