01 - In a bowl, whisk together buttermilk, Cajun seasoning, smoked paprika, garlic powder, onion powder, cayenne pepper, salt, and pepper. Add the chicken breasts, cover, and marinate in the refrigerator for at least 30 minutes (up to 4 hours for extra flavor).
02 - Mix mayonnaise, minced garlic, lemon juice, Dijon mustard, salt, and black pepper in a small bowl until well combined. Refrigerate until ready to use.
03 - In a shallow dish, combine flour and cornstarch. Remove chicken from marinade, allowing excess to drip off, and dredge each breast in the flour mixture, pressing lightly to adhere.
04 - Heat 1 inch of vegetable oil in a large skillet or Dutch oven to 350°F. Fry chicken breasts 5–7 minutes per side, or until golden brown and cooked through (internal temp: 165°F). Drain on a wire rack or paper towels.
05 - Spread garlic aioli on both halves of each toasted bun. Place lettuce on the bottom bun, top with a fried chicken breast, tomato slice, and pickles. Cap with the top bun and serve immediately.