01 - Whisk together buttermilk, hot sauce, garlic powder, onion powder, salt, and black pepper in a large bowl. Submerge chicken thighs completely. Cover and refrigerate for at least 2 hours, up to overnight for optimal flavor penetration.
02 - Combine flour, cornstarch, paprika, baking powder, cayenne pepper, salt, and black pepper in a shallow dish. Mix thoroughly to distribute spices evenly throughout the flour mixture.
03 - Pour vegetable oil into a deep fryer or heavy-bottomed pot. Heat to 350°F, maintaining temperature throughout the frying process for consistent results.
04 - Remove chicken from marinade, allowing excess liquid to drip off. Press each piece firmly into the flour mixture, ensuring a thick, craggy coating adheres to all surfaces. Shake off any loose flour.
05 - Carefully lower coated chicken into hot oil using tongs. Fry for 6 to 8 minutes per piece, turning once halfway through, until deep golden brown and internal temperature reaches 165°F. Transfer to wire rack or paper towels to drain.
06 - Lightly toast burger buns until golden and warm to the touch.
07 - Stir together mayonnaise and hot sauce in a small bowl until fully incorporated. Adjust heat level to taste.
08 - Spread spicy mayonnaise on bottom bun. Layer lettuce, crispy fried chicken, tomato slices, and pickles. Crown with top bun and serve immediately while chicken remains hot and crunchy.