01 - Combine buttermilk, hot sauce, kosher salt, and black pepper in a large bowl. Add chicken thighs, submerge fully, and refrigerate for at least 20 minutes or up to overnight.
02 - In a shallow dish, whisk together all-purpose flour, cornstarch, paprika, garlic powder, onion powder, cayenne pepper, and salt until well distributed.
03 - Remove chicken pieces from marinade, letting excess drip off. Dredge each thigh thoroughly in the flour mixture, pressing to coat. Place coated chicken on a wire rack and rest for 10 minutes to set the coating.
04 - Add vegetable oil to a heavy skillet or Dutch oven until it reaches a 1-inch depth. Heat oil to 350°F (175°C) using a thermometer for accuracy.
05 - Working in batches, carefully place dredged chicken thighs into hot oil. Fry for 5–7 minutes per side, turning once, until golden brown and crisp. Ensure internal temperature reaches 165°F (74°C). Transfer cooked chicken to a clean wire rack to drain.
06 - In a medium bowl, combine 1/2 cup of the hot frying oil with cayenne pepper, brown sugar, chili powder, smoked paprika, garlic powder, and salt. Whisk until smooth and brush hot sauce liberally over both sides of fried chicken using a pastry brush.
07 - Optionally, spread unsalted butter on cut sides of brioche buns and toast in a skillet until golden brown.
08 - Place a piece of sauced hot chicken on each bun bottom. Layer with dill pickle chips and plenty of coleslaw. Crown with the top halves of the buns and serve immediately while hot and crisp.