In a bowl, combine the buttermilk and hot sauce. Add chicken and marinate for at least 1 hour, ideally overnight.

In another bowl, mix the flour, garlic powder, onion powder, paprika, salt, and pepper. Remove chicken from marinade, letting excess drip off, and coat thoroughly in the flour mixture.

Heat oil in a heavy skillet to 350°F. Fry chicken until golden brown and crispy, about 4–5 minutes per side depending on thickness. Rest on a wire rack or paper towel.

Toss shredded romaine with Caesar dressing, Parmesan, black pepper, and a little lemon juice for brightness.

Layer the bottom half of each toasted croissant with Caesar dressing, fried chicken, Caesar salad, shaved Parmesan, and a drizzle of Caesar dressing. Top with the other half of the croissant, brush with melted butter, and add extra Parmesan.