01 - In a mixing bowl, whisk together buttermilk, garlic powder, onion powder, salt, and black pepper. Submerge chicken fillets, cover, and refrigerate for at least 15 minutes and up to 4 hours to tenderize.
02 - Combine all-purpose flour, panko breadcrumbs, and grated Parmesan cheese in a shallow dish. In a separate bowl, beat the eggs until smooth.
03 - Remove chicken from marinade, allowing excess to drip off. Dredge each fillet in the flour mixture, then dip into beaten eggs, and again into flour mixture to ensure a thick, even breading.
04 - Pour vegetable oil to a depth of 1/2 inch into a skillet and heat to 350°F. Fry chicken fillets for 3 to 4 minutes per side, turning once, until golden brown and fully cooked. Transfer to paper towels to drain.
05 - Toss shredded romaine lettuce with Caesar dressing in a bowl. Add shaved Parmesan cheese and gently mix until evenly coated.
06 - Spread optional unsalted butter on cut sides of buns and toast in a skillet until golden brown.
07 - Place a crispy chicken fillet on the bottom half of each toasted bun. Top with Caesar salad mixture, then cap with the top bun.
08 - Serve immediately. Add extra Caesar dressing or lemon wedges on the side if desired.