01 - Slice each chicken breast in half horizontally to create 4 thin fillets of even thickness.
02 - Whisk buttermilk, garlic powder, onion powder, salt, and pepper in a bowl. Add chicken pieces and marinate for at least 15 minutes, up to 4 hours refrigerated for optimal flavor penetration.
03 - Arrange three shallow bowls: one with flour, one with beaten eggs, and one with panko breadcrumbs mixed with grated Parmesan cheese.
04 - Remove chicken from marinade. Dredge each piece in flour, shaking off excess. Dip into egg wash, then press firmly into panko-Parmesan mixture to coat completely and evenly.
05 - Heat ½ inch vegetable oil in a large skillet over medium-high heat. Fry chicken pieces for 3–4 minutes per side until golden brown and cooked through, reaching internal temperature of 165°F. Drain on paper towels.
06 - Lightly toast the cut sides of buns until golden and warm.
07 - Spread Caesar dressing inside each bun. Layer with shredded romaine lettuce, a crispy chicken fillet, additional Caesar dressing, and shaved Parmesan. Finish with freshly ground black pepper.
08 - Close sandwiches and serve immediately while chicken remains crispy.