Miso-simmered mackerel

Make fine cuts with a knife into the mackerel skin. Slice the ginger and cut the polo onion into 2cm thick.

Dip mackerel in boiling water for about 10 seconds, then drop it in ice water and marbled it when the surface becomes white.

Add the drained mackerel, ginger, and [A] to a frying pan and heat it. Once it boils, remove the scum, remove it with aluminum foil, cover it, and heat it.

After simmering for about 10 minutes, remove the aluminum foil and let the liquid evaporate. Once it has thickened, add the chopped leeks and miso, dissolve the miso, and simmer for about 5 minutes until the leeks are tender.
(Be careful not to let it boil from this point on, as this will cause the miso aroma to dissipate.)

Once the green onions are soft and the whole is thick enough, you're done.