01 - In a mixing bowl, combine buttermilk, hot sauce, and Cajun seasoning. Add chicken breasts, cover, and refrigerate for a minimum of 30 minutes or up to 4 hours to develop deeper flavor.
02 - In a separate bowl, blend together flour, corn starch, Cajun seasoning, garlic powder, paprika, salt, and black pepper until fully combined.
03 - Remove chicken from the marinade, allowing any excess to drip off. Thoroughly dredge each breast in the flour mixture, pressing gently to achieve a thick, even coating.
04 - Heat vegetable oil in a deep skillet or Dutch oven to 350°F. Working in batches, fry chicken breasts for 6 to 8 minutes per side, or until golden brown and an instant-read thermometer registers 165°F at the thickest part. Transfer to paper towels to drain.
05 - In a small bowl, whisk together mayonnaise, minced garlic, lemon juice, Dijon mustard, salt, and black pepper. Refrigerate until use.
06 - Toast the brioche buns until golden. Generously spread garlic aioli on the interior halves. Layer with lettuce, fried chicken breast, tomato slices, and optional pickles. Cap with the remaining bun half and serve immediately.