Skin the mackerel, remove the bones and place in a wide bowl. Blend with the dough hook of the mixer. Add cream cheese, melted juice of one lemon, butter, salt and pepper, knead until smooth. Season to taste.
Pour into a can – or a suitable fish mold – smooth. Seal and freeze.
Defrost: Dip the give while still frozen briefly in hot water, turn out onto a plate and thaw, covered, in the refrigerator for about six to eight hours.
Cut thawed pate into slices with a craft knife, arrange in flakes. Garnish with parsley and lemon slices.
Serve with hot toast.