01 - In a mixing bowl, combine buttermilk, garlic powder, onion powder, salt, and black pepper. Submerge chicken fillets in the marinade, cover, and refrigerate for at least 15 minutes or up to 4 hours.
02 - In a shallow dish, blend all-purpose flour, panko breadcrumbs, and grated Parmesan cheese. In a separate bowl, beat the eggs until smooth.
03 - Remove marinated chicken from the bowl. Dust each piece in the flour mixture, dip in beaten egg, then return to the flour mixture, ensuring an even, thick coating.
04 - Pour 1/2 inch of vegetable oil into a deep skillet. Heat oil to 350°F. Fry chicken fillets for 3 to 4 minutes per side until evenly golden brown and fully cooked. Transfer to paper towels for draining.
05 - Toss shredded romaine lettuce in a mixing bowl with Caesar dressing. Add shaved Parmesan and mix gently to combine.
06 - If using, spread unsalted butter onto the cut sides of each bun and toast until lightly golden.
07 - Place one Fried chicken fillet on the bottom half of each bun. Top with Caesar salad, then cover with the top bun. Serve immediately. Optionally, add extra Caesar dressing or lemon wedges.