01 - Place each chicken breast between plastic wrap and pound gently with a meat mallet to 1/2-inch thickness. Season both sides evenly with salt and black pepper.
02 - Combine chicken breasts and buttermilk in a bowl, ensuring all pieces are submerged. Marinate for at least 20 minutes or up to 4 hours in the refrigerator.
03 - In a shallow dish, mix together all-purpose flour, panko breadcrumbs, garlic powder, paprika, and cayenne pepper until well combined.
04 - Remove chicken from buttermilk, allowing excess to drip off. Dredge each piece thoroughly in the flour-breadcrumb mixture, pressing to ensure an even, thick coating.
05 - Heat vegetable oil in a large skillet over medium-high heat to 350°F. Fry breaded chicken breasts for 3 to 4 minutes per side until golden brown and cooked through. Transfer to paper towels to drain excess oil.
06 - In a small bowl, whisk mayonnaise, grated Parmesan, Dijon mustard, minced anchovy, minced garlic, lemon juice, salt, and black pepper until the dressing is smooth and emulsified.
07 - Lightly toast brioche buns or hamburger buns until just golden, then set aside.
08 - Spread Caesar dressing liberally on each bun half. Layer with Romaine lettuce, tomato slices, freshly fried chicken breast, and extra Parmesan if desired. Cover with the top bun and serve immediately.