01 - In a large bowl, whisk together buttermilk, hot sauce, kosher salt, and black pepper. Submerge chicken thighs in the mixture, ensuring even coating. Marinate in the refrigerator for at least 30 minutes, or up to overnight.
02 - In a shallow dish, combine all-purpose flour, cornstarch, paprika, garlic powder, onion powder, cayenne pepper, salt, and black pepper. Mix thoroughly to ensure even distribution of seasonings.
03 - Remove chicken thighs from marinade, allowing excess to drip off. Coat each piece thoroughly in the seasoned flour mixture, pressing gently to create an even layer. Place coated chicken on a wire rack and let rest for 10 minutes.
04 - Heat vegetable oil in a deep skillet or Dutch oven to 350°F. Fry chicken in batches, avoiding crowding the pan. Cook each thigh for 5 to 7 minutes per side until golden brown and internal temperature reaches 165°F. Transfer cooked chicken to a clean wire rack.
05 - In a heatproof bowl, combine cayenne pepper, brown sugar, garlic powder, paprika, chili powder, and salt. Carefully ladle in reserved hot frying oil and whisk until the spicy glaze is smooth and incorporated.
06 - Generously brush the spicy glaze over the freshly fried chicken pieces while they are still hot.
07 - Spread mayonnaise on the bottom halves of each toasted brioche bun, if desired. Place one glazed chicken thigh on each bun, top with pickle chips and a scoop of creamy coleslaw if using, then finish with the top buns.
08 - Serve sandwiches immediately while hot for maximum flavor and texture.