Demi-katsu Don

Okayama's katsudon comes under demi-glace. The first owner of a tonkatsu shop called Ajitsukasa Nomura, which opened in 1931, ate the sauce at the Imperial Hotel in Tokyo and decided the people of Okayama should have it, so he put a pork cutlet on rice with shredded cabbage, poured a dark French sauce over the whole thing and topped it with green peas. It should not work and it has been the city's dish for ninety years.

The sauce is the labour: reduced over days, and every shop that serves demi-katsu don in Okayama guards its own. Around a dozen restaurants make a version, from the originator's counter near the city centre to diners that treat it as ordinary lunch. Ordering plain katsudon in Okayama will usually get you this unless you specify the egg-bound kind.