01 - Combine buttermilk, garlic powder, onion powder, salt, and black pepper in a mixing bowl. Submerge the chicken fillets in the mixture, cover, and refrigerate for at least 15 minutes or up to 4 hours for enhanced tenderness.
02 - In a shallow dish, whisk together all-purpose flour, panko breadcrumbs, and grated Parmesan cheese. In a separate bowl, beat the eggs until well combined.
03 - Remove chicken from marinade. Dredge each fillet in the flour-breadcrumb mixture, dip into beaten eggs, then return to the flour-breadcrumb mixture to ensure a thick, crispy coating.
04 - Heat vegetable oil in a skillet to 350°F (use sufficient oil to create about 1/2 inch depth). Fry coated chicken fillets for 3 to 4 minutes per side until golden brown and internal temperature reaches 165°F. Transfer to paper towels to drain.
05 - Toss shredded romaine lettuce with Caesar dressing in a bowl. Add shaved Parmesan cheese and mix gently to combine.
06 - Spread unsalted butter on cut sides of buns if desired. Toast buns in a skillet or toaster until golden brown.
07 - Arrange a fried chicken fillet on the bottom half of each toasted bun. Top with a generous portion of Caesar salad and cover with the top bun. Serve immediately; offer additional Caesar dressing or lemon wedges on the side if desired.