The dumplings arrive arranged in a ring, and in the middle of the ring there is a heap of boiled bean sprouts. Neither of those is a decorative decision.

The ring exists because of a pan. In the stall days the cooking was done in an ordinary domestic frying pan, and laying the dumplings around the curve of it left a circle of empty metal in the centre. Somebody put sprouts there. They cut the richness, and with them on the plate you can get through considerably more dumplings than you otherwise would, which is presumably why the practice stuck.

The filling runs heavy on cabbage and comes out sweet because of it. Some shops change where they buy the cabbage as the seasons move, and the proportions of pork and garlic are a matter of local argument.

It begins just after the war. A stall near Hamamatsu station is said to have worked out its recipe by questioning soldiers coming home from Manchuria and elsewhere on the continent, and cooking what they described. So a dish learned on the far side of a sea was reshaped, within a few years, by the diameter of the only pan available. Almost everything people now consider essential about it — the circle, the sprouts, the sweetness — came from that constraint rather than from anybody's intention.