01 - Blend buttermilk, garlic powder, onion powder, salt, and black pepper in a mixing bowl. Add chicken fillets, coating evenly. Cover and refrigerate for at least 15 minutes, up to 4 hours for optimal tenderness.
02 - In a shallow dish, combine all-purpose flour, panko breadcrumbs, and grated Parmesan cheese. In a separate bowl, beat eggs thoroughly.
03 - Remove chicken from marinade. Coat each fillet in flour mixture, dip in egg wash, then return to flour mixture for a final layer.
04 - Heat 1/2 inch vegetable oil in a skillet to 350°F. Fry chicken fillets 3 to 4 minutes per side until golden brown and internal temperature reaches 165°F. Transfer to paper towels to drain excess oil.
05 - In a clean bowl, toss shredded romaine lettuce with Caesar dressing. Fold in shaved Parmesan gently until evenly coated.
06 - Optionally, spread butter on bun interiors and toast until golden in a skillet or toaster. Place fried chicken on bottom halves of buns, top with Caesar salad mixture, and finish with upper bun halves.
07 - Serve sandwiches immediately. Offer additional Caesar dressing or lemon wedges alongside if desired.