01 - Combine chicken, pickle brine, and hot sauce in a resealable bag. Refrigerate for at least 1 hour, up to overnight.
02 - Heat vegetable oil in a heavy-bottomed pot or deep skillet to 350°F.
03 - Whisk together flour, cornstarch, paprika, garlic powder, onion powder, cayenne, salt, and pepper in a shallow dish.
04 - Remove chicken from brine, allowing excess to drip off. Dredge thoroughly in flour mixture, coating all sides evenly.
05 - Fry chicken in batches for 5-7 minutes per side until golden brown and internal temperature reaches 165°F. Drain on wire rack.
06 - Mix mayonnaise and Dijon mustard in a small bowl until smooth and combined.
07 - Lightly toast buns and spread mayo-mustard sauce on both cut sides.
08 - Place fried chicken on bottom buns, top with lettuce and pickle slices, and finish with bun tops. Serve immediately.