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 or up to 4 hours for enhanced tenderness.
02 - Combine flour, panko breadcrumbs, and grated Parmesan in a shallow bowl. In a separate bowl, beat the eggs thoroughly.
03 - Remove marinated chicken from the bowl, letting excess liquid drip off. Dredge each fillet in flour mixture, then dip in beaten egg, and coat again in the flour mixture, pressing gently for adhesion.
04 - Pour enough vegetable oil into a skillet to reach 1/2 inch depth and heat to 350°F. Fry the chicken fillets in batches, 3 to 4 minutes per side, until golden brown and cooked through. Transfer to a paper towel-lined plate to drain excess oil.
05 - Toss shredded romaine with Caesar dressing until evenly coated. Add shaved Parmesan and fold gently to combine.
06 - If desired, spread unsalted butter on the cut sides of each bun. Toast in a skillet until golden and crisp.
07 - Place one fried chicken fillet on the bottom half of each toasted bun. Top generously with Caesar salad and cover with the remaining bun halves. Serve immediately with optional additional Caesar dressing or lemon wedges.