01 - Whisk buttermilk, hot sauce, salt, pepper, garlic powder, and paprika in a bowl until thoroughly combined. Add chicken thighs, turning to coat completely. Cover and refrigerate for at least 20 minutes or overnight for maximum flavor penetration.
02 - Combine flour, cornstarch, salt, paprika, cayenne pepper, onion powder, and garlic powder in a large bowl. Whisk until evenly distributed.
03 - Remove chicken from marinade, allowing excess liquid to drip off. Press each piece firmly into the flour mixture, ensuring thick, even coating on all sides. Place coated pieces on a wire rack.
04 - Pour vegetable oil into a deep skillet or Dutch oven to a depth of 1 inch. Heat to 350°F over medium-high heat.
05 - Working in batches to avoid overcrowding, fry chicken for 5 to 7 minutes per side until golden brown and crispy. Internal temperature should reach 165°F. Transfer to wire rack or paper towels to drain.
06 - Toss shredded cabbage, grated carrot, mayonnaise, apple cider vinegar, salt, and pepper in a bowl until cabbage is evenly coated.
07 - Lightly toast burger buns if desired. Spread mayonnaise on bottom bun, layer lettuce, fried chicken thigh, slaw, and pickle slices. Top with remaining bun half.
08 - Serve immediately while chicken is hot and coating remains crispy.