Marinate the chicken breasts in buttermilk for at least 1 hour or up to overnight in the refrigerator.

In a shallow dish, combine flour, garlic powder, onion powder, paprika, salt, and black pepper.

Remove chicken from the buttermilk, letting excess drip off, then coat thoroughly in the seasoned flour mixture. Set aside.

Heat vegetable oil in a large skillet over medium-high heat until it reaches about 350°F.

Carefully fry the breaded chicken for 5-7 minutes on each side until golden brown and cooked through (internal temperature should reach 165°F).

Transfer chicken to a paper towel-lined plate to drain excess oil and let rest.

In a medium bowl, whisk together mayonnaise, lemon juice, Dijon mustard, minced garlic, and Parmesan cheese until smooth. Season with salt and pepper to taste.

Toast the bread slices until golden and crispy.

Spread the Caesar dressing generously on one side of each toast slice.

Layer chopped romaine lettuce on two slices of the bread.

Place the crispy chicken on top of the lettuce. Add sliced tomatoes or crispy bacon if desired.

Sprinkle additional Parmesan cheese over the chicken.

Top with the remaining bread slices, dressing side down, and press gently to adhere.

Slice sandwiches diagonally and serve immediately.