Marinate the Chicken : In a bowl, combine buttermilk and hot sauce.Add chicken, cover, and refrigerate for at least 1 hour (or up to overnight).
Prepare the Slaw : In a large bowl, whisk together mayonnaise, vinegar, sugar, salt, and pepper.Toss in cabbage and carrots. Mix well, cover, and refrigerate until serving.
Set Up the Breading Station : In a shallow dish, mix flour, cornstarch, paprika, garlic powder, onion powder, salt, and black pepper.
Bread the Chicken : Remove chicken from buttermilk, letting excess drip off. Dredge in flour mixture, pressing gently to coat.For extra crispy chicken, dip back into buttermilk and then coat again in flour mixture.
Fry the Chicken : Heat 2 inches of oil in a deep skillet or Dutch oven to 350°F (175°C).Fry chicken in batches for 5–7 minutes per side, or until golden brown and internal temperature reaches 165°F (74°C).Transfer to a wire rack set over a baking sheet to drain.
Make the Nashville Hot Oil : In a heatproof bowl, mix cayenne, brown sugar, paprika, chili powder, garlic powder, and salt. Carefully ladle in 1/2 cup hot frying oil from the skillet and whisk until smooth.
Coat the Chicken : Brush or spoon the hot oil generously over the fried chicken on both sides.
Assemble the Sandwiches : Place a piece of chicken on the bottom half of each toasted bun.Top with slaw, pickles, and bun tops.