01 - Combine buttermilk, hot sauce, kosher salt, and black pepper in a large bowl. Add chicken thighs and ensure they are fully submerged. Marinate for at least 20 minutes or refrigerate overnight for enhanced tenderness.
02 - In a shallow dish, thoroughly mix all-purpose flour, cornstarch, paprika, garlic powder, onion powder, cayenne pepper, and salt for the coating.
03 - Remove chicken from marinade, allowing excess liquid to drip off. Dredge each thigh in the flour mixture, pressing firmly so the coating adheres well. Transfer to a wire rack and let rest for 10 minutes to set the coating.
04 - Pour vegetable oil into a heavy skillet or Dutch oven to a depth of 1 inch. Heat oil to 350°F (175°C), monitoring temperature closely for optimal frying.
05 - Fry the coated chicken thighs in batches for 5 to 7 minutes per side until golden brown, crisp, and internal temperature reaches 165°F (74°C). Transfer to a wire rack to drain excess oil.
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 blended into a smooth, spicy paste.
07 - While chicken is still hot, brush each piece generously with the prepared Nashville hot sauce, coating both sides for maximum flavor.
08 - Optional: Spread cut sides of brioche buns with unsalted butter and toast in a skillet until golden and lightly crisped.
09 - Place sauced chicken thighs on the base of each brioche bun. Top with dill pickle chips and a generous scoop of coleslaw. Cap with the top bun and serve immediately for best texture.