01 - Combine buttermilk, garlic powder, onion powder, salt, and black pepper in a bowl. Submerge chicken fillets, cover, and refrigerate for at least 15 minutes or up to 4 hours.
02 - In a shallow dish, mix flour, panko breadcrumbs, and grated Parmesan. In another bowl, beat the eggs until smooth.
03 - Remove chicken from marinade. Coat each piece in the flour mixture, then dip in beaten eggs, and coat again with the flour mixture, ensuring an even, thick crust.
04 - Pour 1/2 inch vegetable oil into a skillet and heat to 350°F. Fry chicken fillets for 3 to 4 minutes per side until golden and fully cooked. Transfer onto paper towels to drain excess oil.
05 - Toss shredded romaine lettuce with Caesar dressing in a bowl. Sprinkle in shaved Parmesan and gently combine.
06 - (Optional) Spread butter on cut sides of buns. Toast in a skillet until golden and crisp.
07 - Place a fried chicken fillet on each bottom bun. Top with Caesar salad mixture and cover with top bun. Serve immediately with extra dressing or lemon wedges if desired.