01 - Whisk together buttermilk, hot sauce, garlic powder, onion powder, salt, and pepper in a large bowl. Submerge chicken thighs completely, cover, and refrigerate for minimum 2 hours or overnight for optimal flavor penetration.
02 - Combine flour, cornstarch, paprika, baking powder, cayenne, salt, and black pepper in a shallow dish. Mix thoroughly to ensure even distribution of spices and leavening agents.
03 - Pour vegetable oil into deep fryer or heavy-bottomed pot. Bring temperature to 350°F, maintaining steady heat throughout cooking process.
04 - Lift chicken from marinade, allowing excess liquid to drip off. Press each piece firmly into flour mixture, turning to coat completely and creating a thick, craggy surface for maximum crunch.
05 - Lower coated chicken carefully into hot oil using tongs. Fry 6–8 minutes per piece, turning once halfway through, until deep golden brown and internal temperature reaches 165°F. Transfer to wire rack to drain.
06 - Lightly toast cut sides of burger buns until golden and warm to the touch.
07 - Blend mayonnaise with hot sauce in small bowl until smooth. Adjust heat level to preference.
08 - Spread spicy mayo on bottom bun. Layer lettuce leaf, fried chicken fillet, tomato slice, and pickles. Cap with top bun and serve immediately while chicken remains crispy.