Clean the mackerel and wipe carefully with a dry, clean cloth; wash
them lightly with another cloth dipped in vinegar; wrap each in a
coarse linen cloth (floured) basted closely to the shape of the fish.
Put them into a pot with enough salted water to cover them, and boil
them gently for three quarters of an hour. Drain them well. Take a
teacupful of the water in which they were boiled, and put into a
saucepan with a tablespoonful of walnut catsup, some anchovy paste or
sauce, and the juice of half a lemon. Let this boil up well and add a
lump of butter the size of an egg, with a tablespoonful browned flour
wet in cold water. Boil up again and serve in the sauce-boat. This
makes a brown sauce. You can substitute egg-sauce if you like. Garnish
with parsley and nasturtium blossoms.