01 - Combine buttermilk, hot sauce, salt, and ground black pepper in a large mixing bowl. Submerge chicken thighs, ensuring they are evenly coated. Marinate for at least 20 minutes or up to overnight in the refrigerator.
02 - In a shallow dish, whisk together all-purpose flour, cornstarch, paprika, garlic powder, onion powder, cayenne pepper, and salt until fully combined.
03 - Remove chicken thighs from the marinade, allowing excess liquid to drip off. Coat each piece thoroughly in the flour mixture, pressing to adhere, and set on a wire rack for 10 minutes.
04 - In a heavy skillet or Dutch oven, pour in vegetable oil to a depth of 1 inch. Heat over medium-high heat until temperature reaches 350°F.
05 - Working in batches, fry chicken thighs for 5 to 7 minutes per side, or until deeply golden and crisp. Internal temperature must reach 165°F. Transfer to a wire rack to drain.
06 - In a medium bowl, mix 1/2 cup of hot frying oil with cayenne pepper, brown sugar, chili powder, smoked paprika, garlic powder, and salt until smooth. Generously brush both sides of each fried chicken thigh with the hot sauce.
07 - Spread unsalted butter on the cut sides of the brioche buns. Toast in a skillet over medium heat until golden and crisp, if desired.
08 - Set the sauced chicken thigh on the bottom bun. Top with dill pickle chips and a generous scoop of coleslaw. Close with the top bun and serve immediately.