01 - In a large mixing bowl, whisk together buttermilk, hot sauce, salt, and black pepper. Submerge chicken thighs in the marinade, cover, and refrigerate for at least 20 minutes or up to overnight.
02 - Combine flour, cornstarch, paprika, garlic powder, onion powder, cayenne pepper, and salt in a shallow dish. Mix thoroughly to ensure even seasoning.
03 - Lift chicken thighs from the marinade, allowing excess to drip off. Dredge each piece in the seasoned flour mixture, pressing firmly to adhere. Arrange coated pieces 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 to 350°F.
05 - Fry chicken thighs in batches for 5 to 7 minutes per side until golden brown, crispy, and the internal temperature reaches 165°F. Transfer to a clean wire rack to drain.
06 - In a bowl, whisk together 1/2 cup hot frying oil, cayenne pepper, brown sugar, chili powder, smoked paprika, garlic powder, and salt until smooth. Generously brush hot sauce over both sides of the fried chicken.
07 - Optional: Butter the cut sides of the brioche buns and toast them in a skillet until golden brown.
08 - Layer sauced fried chicken, pickle chips, and a generous scoop of coleslaw on each bun base. Place the top bun and serve immediately.