Basic boiled fish (simmered mackerel with miso)

Cut the mackerel and wipe off any water.
Put mirin, sake, soy sauce, sugar and vinegar in a small pot and bring to a boil over medium heat.
Add the mackerel and green onions and cover with wet paper as a dispenser.
Simmer over medium heat for about 7 minutes, pouring the broth on occasion.
Turn off the heat, melt in the miso, and simmer for another minute and you're done.