Pound the chicken breasts lightly to even thickness.
Marinate chicken in buttermilk for at least 30 minutes.
Mix flour, garlic powder, paprika, salt, and pepper in a shallow dish.
Heat olive oil in a skillet over medium heat.
Dredge chicken in flour mixture, pressing lightly to coat.
Fry chicken until golden and cooked through, about 5–6 minutes per side.
Mix mayonnaise with Caesar dressing in a small bowl.
Spread dressing mix on buns, add lettuce and parmesan.
Place crispy chicken on top, then close sandwich and serve.