01 - Combine buttermilk, hot sauce, kosher salt, and black pepper in a large mixing bowl. Add chicken thighs and submerge fully in the marinade. Cover and refrigerate for at least 20 minutes or up to overnight.
02 - In a shallow dish, thoroughly mix the all-purpose flour, cornstarch, paprika, garlic powder, onion powder, cayenne pepper, and salt.
03 - Remove chicken from marinade, allowing excess liquid to drain. Dredge each thigh in the flour mixture, pressing firmly to ensure an even coating. Transfer to a wire rack and let rest 10 minutes.
04 - Pour vegetable oil into a heavy skillet or Dutch oven to a 1-inch depth. Heat oil over medium-high heat until it reaches 350°F (175°C).
05 - Using tongs, fry chicken thighs in batches for 5 to 7 minutes per side until golden brown and crispy, ensuring the internal temperature reads 165°F (74°C). Place fried chicken on a clean wire rack to drain.
06 - Carefully whisk together 1/2 cup of hot frying oil, cayenne pepper, brown sugar, chili powder, smoked paprika, garlic powder, and salt in a medium heatproof bowl until smooth.
07 - Generously brush the hot sauce over both sides of each fried chicken thigh, ensuring a uniform layer.
08 - Optional: Spread unsalted butter on the cut sides of brioche buns and toast in a skillet until golden brown.
09 - Place a sauced chicken thigh on the bottom half of each bun. Top with dill pickle chips and a generous scoop of coleslaw. Close with the upper bun and serve immediately.