Preheat oven to 425°F. Line a metal baking sheet with foil. Coat generously with cooking spray.
Place cornflake crumbs onto a plate.
In a medium bowl, combine ground chicken, mustard, paprika, garlic powder, onion powder, salt, pepper, and cayenne pepper until well combined. Form into 8 patties.
Bread patties with cornflake crumbs, pressing down to ensure each is well coated on both sides.
Place on prepared baking sheet. Coat generously with cooking spray.
Bake for 18 minutes. Turn patties; bake for an additional 5 minutes.
Heat a frying pan over medium heat. Toast buns for 2 minutes or until toasted.
To assemble, lightly coat toasted sides of the buns with mayonnaise. Top with crispy chicken patty and shredded romaine. Serve immediately.