01 - Whisk together buttermilk, hot sauce, kosher salt, and black pepper in a large mixing bowl. Submerge chicken thighs, cover, and refrigerate for at least 20 minutes, or up to overnight for optimal tenderness.
02 - In a shallow dish, thoroughly blend all-purpose flour, cornstarch, paprika, garlic powder, onion powder, cayenne pepper, and salt until homogenous.
03 - Remove chicken from marinade, allowing excess to drip off. Dredge each thigh in the flour mixture, ensuring an even coating. Place on a wire rack for 10 minutes to set the crust.
04 - Pour vegetable oil into a heavy skillet or Dutch oven to a depth of one inch. Heat over medium-high until oil temperature reaches 350°F.
05 - Fry chicken thighs in batches, 5 to 7 minutes per side, until golden brown and crispy. Internal temperature should reach 165°F. Transfer cooked chicken to 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, whisking until smooth. Generously brush mixture over both sides of the fried chicken.
07 - If desired, spread unsalted butter on the cut sides of brioche buns and toast in a skillet until golden brown.
08 - Position sauced chicken thighs on each bun base. Layer with dill pickle chips and a generous scoop of coleslaw. Cap with the top brioche bun and serve immediately.