01 - Whisk together buttermilk, hot sauce, garlic powder, onion powder, salt, and pepper in a large bowl. Add chicken thighs, submerge 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 until evenly blended.
03 - Pour vegetable oil into deep fryer or heavy-bottomed pot. Heat to 350°F, maintaining consistent temperature throughout frying process.
04 - Lift chicken from marinade, allowing excess liquid to drip off. Press each piece firmly into flour mixture, turning to coat completely and pressing to create thick, craggy coating that adheres well.
05 - Lower coated pieces carefully 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 cut sides of burger buns until golden and warm to the touch.
07 - Stir together mayonnaise and hot sauce in small bowl until thoroughly combined for spicy variation.
08 - Spread mayonnaise on toasted bottom buns. Layer lettuce, fried chicken, tomato slices, and pickles. Crown with top buns and serve immediately while hot.