Legend has it is that Louis Lassen invented the hamburger on this spot. Some 110 years later, the Lassen family still serves his invention, and still cooks them in the unusual gas broilers that Lassen designed - the patties are suspended on vertical racks, allowing the grease to drip down their sides while they cook. The ritual includes serving the burger with tomato, onion, cheese and toasted bread, which, one can argue, is evidence that the place predates the custom of using buns. Condiment-lovers, note: Asking for ketchup is strictly taboo.