01 - Combine buttermilk, garlic powder, onion powder, salt, and black pepper in a mixing bowl. Submerge chicken fillets, cover, and refrigerate for a minimum of 15 minutes (up to 4 hours for improved tenderness).
02 - In a shallow bowl, blend together flour, panko breadcrumbs, and grated Parmesan. In a separate bowl, whisk eggs until smooth.
03 - Remove chicken fillets from marinade, allowing excess liquid to drip off. Coat each fillet in the flour mixture, dip in beaten egg, then dredge again in the flour mixture for an enhanced crispy crust.
04 - Pour vegetable oil into a skillet to a 1/2-inch depth and heat to 350°F. Fry breaded chicken for 3 to 4 minutes per side until golden brown and thoroughly cooked. Transfer to paper towels to absorb excess oil.
05 - Toss shredded romaine lettuce with Caesar dressing in a clean bowl. Fold in shaved Parmesan cheese until evenly distributed.
06 - To enhance flavor, spread unsalted butter on the cut side of each bun and toast in a skillet or on a griddle until golden brown.
07 - Place fried chicken fillet on the lower half of each toasted bun. Top with dressed romaine salad, then cap with the remaining bun half. Serve immediately with optional additional Caesar dressing or lemon wedges.