When in season and full of roe, is the time for this process. Take
a dozen mackerel, split them down the back from the head downwards,
and leaving the thin side connected for an inch with the tail; take
out the roes and livers, some of which will be beautiful if otherwise
cured and preserved, remove the gills and refuse, wiping clean out.
Rub the insides lightly with good olive oil, and let them remain skin
side downwards three hours. Boil for a quarter of an hour the following
ingredients, and skim well:
Rock salt or common salt 1 lb.
Bay salt 1 lb.
Saltpetre ¼ lb.
Coarse sugar 1 lb.
Water 1 gall.