01 - In a large bowl, whisk together buttermilk, hot sauce, garlic powder, onion powder, salt, and pepper. Add chicken thighs, ensuring they are fully submerged. Cover and refrigerate for at least 2 hours, up to overnight for maximum flavor penetration.
02 - In a shallow dish, combine flour, cornstarch, paprika, baking powder, cayenne pepper, salt, and black pepper. Mix thoroughly to distribute spices evenly.
03 - Pour vegetable oil into a deep fryer or heavy-bottomed pot. Heat to 350°F, maintaining consistent temperature throughout frying.
04 - Remove chicken from marinade, allowing excess liquid to drip off. Press each piece firmly into the flour mixture, turning to coat completely and pressing to create a thick, craggy coating that adheres well.
05 - Carefully lower coated chicken into hot oil. Fry for 6 to 8 minutes per piece, turning once halfway through, until deep golden brown and cooked through to internal temperature of 165°F. Transfer to wire rack or paper towels to drain.
06 - Lightly toast burger buns until golden brown for added texture and to prevent sogginess.
07 - Combine mayonnaise with hot sauce in a small bowl, adjusting spice level to preference.
08 - Spread spicy mayo on bottom bun. Layer with lettuce leaf, fried chicken fillet, tomato slice, and pickle chips. Top with remaining bun and serve immediately while hot.