Remove the roes, wash the fish, put them into the pan with just sufficient hot water to cover and add salt to taste.
Bring the water gently to near boiling-point, then reduce heat and cook very gently for about 10 min.
If cooked too quickly, or too long, the skin is liable to crack and spoil the appearance of the fish.
The fish is sufficiently cooked when the skin becomes loose from the flesh.
Drain well, place the mackerel on a hot dish, pour a little parsley sauce over and serve the remainder of the sauce separately.