01 - In a large bowl, whisk together buttermilk, hot sauce, kosher salt, and black pepper. Submerge chicken thighs in the mixture and marinate for a minimum of 20 minutes or up to overnight in the refrigerator.
02 - In a shallow dish, combine all-purpose flour, cornstarch, paprika, garlic powder, onion powder, cayenne pepper, and salt until thoroughly blended.
03 - Remove chicken thighs from marinade, allowing excess to drip away. Dredge each piece in the flour mixture, pressing firmly to ensure an even coating. Transfer to a wire rack and let rest for 10 minutes.
04 - Pour vegetable oil into a heavy skillet to a depth of 1 inch. Heat oil over medium-high heat to 350°F (175°C).
05 - Working in batches, fry chicken thighs for 5 to 7 minutes per side until golden brown and crispy, ensuring internal temperature reaches 165°F (74°C). Set on a wire rack to drain.
06 - In a medium bowl, combine 1/2 cup hot frying oil with cayenne pepper, brown sugar, chili powder, smoked paprika, garlic powder, and salt. Whisk until homogenized and smooth.
07 - Brush the spicy Nashville hot sauce generously over both sides of the fried chicken using a pastry brush.
08 - Spread unsalted butter on the cut sides of the brioche buns. Lightly toast in a skillet over medium heat until just golden.
09 - Place a piece of sauced chicken on each bun base, top with dill pickle chips and a generous portion of coleslaw. Finish with the top bun and serve immediately.