Japanese-style Belly Pork with Dancing Bonito

We tend to think of Japanese food as being elegant and formal, but they have a whole tradition of earthy peasant food which is now starting to be seen in the West Here, the pork is simmered for a long time until meltingly tender, its fattiness cut with generous additions of Colman’s mustard.

I always used to use Japanese mustard for this dish until I discovered that the Japanese import mustard from England only to do something mysterious to it before putting it in s