01 - In a large bowl, whisk together buttermilk, hot sauce, kosher salt, and black pepper. Submerge the chicken thighs and marinate for at least 20 minutes, or cover and chill overnight for deeper flavor.
02 - In a shallow dish, combine all-purpose flour, cornstarch, paprika, garlic powder, onion powder, cayenne pepper, and salt until thoroughly mixed.
03 - Remove chicken from the marinade, allowing excess to drip away. Dredge chicken thoroughly in the flour mixture, pressing to ensure an even coating. Transfer to a wire rack and let the coating set for 10 minutes.
04 - Pour vegetable oil into a heavy skillet or Dutch oven to a 1-inch depth. Preheat oil to 350°F (use a thermometer for accuracy).
05 - Working in batches, fry chicken thighs for 5 to 7 minutes per side until golden brown and an instant-read thermometer registers 165°F at the center. Transfer fried chicken to a wire rack to drain.
06 - In a medium bowl, whisk 1/2 cup of hot frying oil with cayenne pepper, brown sugar, chili powder, smoked paprika, garlic powder, and salt until smooth and emulsified.
07 - Generously brush the spicy sauce over both sides of each fried chicken thigh while still hot.
08 - Spread unsalted butter on the cut sides of brioche buns and toast in a skillet until golden and crisp, if desired.
09 - Layer the sauced chicken thighs on the bottom halves of toasted buns. Top each with dill pickle chips and a generous scoop of coleslaw. Cap with the top bun and serve immediately.