01 - Combine chicken, pickle brine, and hot sauce in a resealable bag or bowl. Marinate in refrigerator for at least 1 hour, up to overnight for maximum flavor penetration.
02 - Whisk together flour, cornstarch, paprika, garlic powder, onion powder, cayenne, salt, and black pepper in a shallow dish until evenly distributed.
03 - Pour vegetable oil into a heavy-bottomed pot or deep skillet. Heat to 350°F, maintaining consistent temperature throughout frying process.
04 - Remove chicken from brine, allowing excess liquid to drip off. Press firmly into flour mixture, turning to coat all sides evenly and thoroughly.
05 - Place chicken pieces in hot oil, working in batches to avoid overcrowding. Fry 5–7 minutes per side until golden brown and internal temperature reaches 165°F. Transfer to wire rack to drain.
06 - Mix mayonnaise and Dijon mustard in a small bowl until fully combined and smooth.
07 - Lightly toast brioche or potato buns until golden, then spread prepared mayo-mustard sauce on both cut sides.
08 - Place fried chicken on bottom bun, layer with shredded lettuce and pickle slices. Top with remaining bun half and serve immediately while hot.