In a large bowl, whisk together the buttermilk and hot sauce. Add the chicken thighs and ensure they are fully submerged. Cover and refrigerate for at least 4 hours or overnight.

Prepare the Dredge

In a separate bowl, mix together the flour, cornstarch, salt, black pepper, and paprika.

Coat the Chicken

Remove the chicken from the buttermilk, allowing excess to drip off. Dredge each piece in the flour mixture, pressing firmly to ensure full coating. Set aside on a wire rack.

Fry the Chicken

Heat the vegetable oil in a deep pot or skillet to 350°F (175°C). Fry the chicken pieces in batches for 5–7 minutes each side, or until golden brown and internal temperature reaches 165°F (74°C). Transfer to a wire rack over paper towels to drain. Reserve 1/4 cup of the hot frying oil for the hot spice.

Nashville Hot Spice Oil

Make Hot Oil Mixture

In a heatproof bowl, whisk together cayenne, brown sugar, paprika, garlic powder, and salt. Carefully pour in the reserved 1/4 cup of hot frying oil and stir until well mixed.

Glaze the Chicken

Brush or spoon the hot spice oil generously over the fried chicken pieces while they are still warm. Set aside.

Coleslaw

Make the Dressing

In a small bowl, whisk together mayonnaise, apple cider vinegar, sugar, salt, and pepper.

Toss the Slaw

In a large bowl, combine shredded cabbage and carrots. Pour the dressing over and toss until evenly coated. Chill in refrigerator until ready to use.

Assembly

Assemble the Sandwich

Toast the sandwich buns lightly. Spread ranch dressing on the bottom half. Add a generous portion of coleslaw, top with one piece of Nashville hot chicken, a few slices of bread and butter pickles, then the top bun. Repeat for all sandwiches.