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 at least 2 hours or overnight for maximum flavor penetration.
02 - Combine flour, cornstarch, paprika, baking powder, cayenne, salt, and black pepper in a shallow dish. Whisk thoroughly to ensure even distribution of spices and leavening agents.
03 - Pour vegetable oil into a deep fryer or heavy-bottomed pot. Heat to 350°F, maintaining temperature throughout frying for consistent crisping.
04 - Lift chicken from marinade, allowing excess liquid to drip off. Press each piece firmly into the flour mixture, coating completely and creating a thick, craggy layer for maximum crunch.
05 - Lower coated chicken carefully into hot oil. Fry 6–8 minutes per piece, turning once, 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 - Stir together mayonnaise and hot sauce in a small bowl until smooth and evenly blended.
08 - Spread spicy mayo on bottom bun. Layer lettuce, crispy fried chicken, tomato slices, and pickles. Crown with top bun and serve immediately.