01 - In a large bowl, whisk together buttermilk, hot sauce, kosher salt, and black pepper. Submerge chicken thighs and refrigerate for at least 20 minutes or up to overnight.
02 - In a shallow dish, thoroughly blend all-purpose flour, cornstarch, paprika, garlic powder, onion powder, cayenne pepper, and salt.
03 - Lift each thigh from the marinade, allowing excess to drain. Dredge in the seasoned flour mixture, pressing firmly to ensure even coverage. Rest on a wire rack for 10 minutes.
04 - Pour vegetable oil into a heavy skillet to a depth of 1 inch. Preheat oil to 350°F.
05 - Fry chicken thighs in batches for 5 to 7 minutes per side until golden, crisp, and an internal temperature of 165°F is reached. Transfer to a clean wire rack.
06 - Combine 1/2 cup hot frying oil with cayenne pepper, brown sugar, chili powder, smoked paprika, garlic powder, and salt in a medium bowl. Whisk until a smooth emulsion forms.
07 - Brush the hot sauce liberally onto both sides of the fried chicken thighs.
08 - Spread unsalted butter on the cut sides of brioche buns; toast in a skillet over medium heat until golden.
09 - Place glazed chicken thigh on each bun base. Top with pickle chips and a generous portion of coleslaw. Cap with the top bun and serve immediately.