It is cut frozen and eaten frozen. The first moment is hard and almost tasteless, a cold shaving on the tongue. Then it begins to give, the fat comes out of it, and only at that point does it start to taste of salmon at all. The dish changes while you are eating it, which is not something most food does.

The method is Ainu. The name is usually explained as two words joined: one meaning to melt, one meaning food. Salmon was buried in the snow through the winter and taken out as needed, cut thin while still hard. Nothing about that was a technique so much as an arrangement with the weather, which in that part of the world could be relied on.

It is also a way of making raw fish safe. Parasites in the flesh do not survive freezing, and in a country without refrigeration this was the answer to the question of how to eat salmon raw in February. The reasoning was arrived at long before anyone could have explained it.

There are freezers now, everywhere, and the problem the dish solved has stopped existing. The dish did not stop. It still arrives frozen, on a cold plate, and people still sit and wait for it to soften rather than ordering something that is ready.