01 - Whisk together buttermilk, hot sauce, garlic powder, onion powder, salt, and pepper in a large bowl. Add chicken thighs, ensuring they're fully coated. 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. Mix thoroughly to distribute spices evenly throughout the coating mixture.
03 - Pour vegetable oil into a deep fryer or heavy-bottomed pot. Heat to 350°F, maintaining temperature throughout the frying process for optimal crispiness.
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 will crisp during frying.
05 - Carefully lower coated chicken into the hot oil. Fry for 6-8 minutes per piece, turning once halfway through, until golden brown and crispy. Verify doneness with an internal temperature of 165°F. Transfer to a wire rack or paper towels to drain.
06 - Lightly toast the cut sides of burger buns until golden and warm, creating a sturdy base that won't become soggy from the sauce and juices.
07 - Combine mayonnaise with hot sauce in a small bowl, adjusting ratio to taste preference for a spicy mayo that complements the crispy chicken.
08 - Spread spicy mayo on the bottom bun. Layer lettuce, followed by the fried chicken fillet, tomato slices, and pickles. Cap with the top bun and serve immediately while hot and crispy.