01 - Combine buttermilk, garlic powder, onion powder, salt, and pepper in a mixing bowl. Submerge chicken fillets, cover, and refrigerate for at least 15 minutes or up to 4 hours.
02 - In a shallow bowl, mix flour, panko breadcrumbs, and grated Parmesan. In a separate bowl, whisk the eggs until smooth.
03 - Remove each fillet from the marinade. Coat in flour mixture, dip into egg, then coat again in flour mixture for an extra-crispy layer.
04 - Heat 1/2 inch of vegetable oil in a skillet to 350°F. Fry chicken fillets 3 to 4 minutes per side until golden brown and internal temperature reaches 165°F. Drain on paper towels.
05 - In a mixing bowl, toss shredded romaine with Caesar dressing. Sprinkle with shaved Parmesan and gently fold to combine.
06 - Optional: Spread butter on cut sides of buns and toast on a skillet until golden.
07 - Place fried chicken on the base of each bun. Top with Caesar salad and finish with the top bun.
08 - Serve sandwiches immediately. Accompany with extra Caesar dressing or lemon wedges if desired.