The kroket itself started life as a fancy French idea, but the Dutch habit of jamming a whole one, still hot from the fryer, straight into a bread roll is a home-grown lunch counter invention.
A cylindrical croquette of ragout bound with a stiff roux is breaded and deep-fried until crisp, then wedged whole into a soft white roll with mustard. Snack bars and market lunch counters across Rotterdam and The Hague sell it as a fast, standing-up lunch.