Clean the mackerel well, and let them lie a short time in vinegar and water. Then put them into the fish-kettle with cold water and a handful of salt. Boil them slowly. If small, they will be sufficiently cooked in twenty minutes. When the eye starts and the tail splits they are done. Take them up immediately on finding them boiled enough. If they stand any time in the water they will break.
They are eaten with mustard.
For boiling, choose those that have soft roes.
Another way is to put them in cold salt and water, and let them warm gradually for an hour. Then give them one hard boil, and they will be done.