On the nineteenth of November, 2008, the US Navy base at Yokosuka handed the city a recipe. It was the traditional navy hamburger, and the handover was timed to the tenth anniversary of Yokosuka navy curry, presented by the base and the Japanese maritime self-defense force as a gesture of friendship and a joint effort to do something for the town.

The city named the result the Yokosuka Navy Burger, and shops around the base began selling it from January of the following year. The certification conditions are austere: lean beef, one hundred percent, cooked simply enough that nothing interferes with the taste of the meat itself.

Fresh onion and tomato go on the burger. Ketchup and mustard do not go anywhere near it. Those are put on the table and the person eating applies as much or as little as they want, which is described as the traditional American way of doing it.

The reason a recipe was worth handing over at all is that Yokosuka has a claim to being where this food entered Japan. In the late 1940s hamburgers were served at the EM Club near Shioiri station, with a big band playing, and ordinary Japanese civilians ate one for the first time.