COLD MACKEREL, VINAIGRETTE

Clean the mackerel, leaving the head on, wrap it in a piece of cheesecloth, and boil in boiling salted water until tender.

The water should contain a little vinegar. Put the tarragon vinegar into a basin, add the mustard, salt, olive oil, parsley, shallots, gherkins, and capers. Remove the cloth from the fish, then lay the mackerel in an earthenware dish, pour the sauce over it and let it marinate thoroughly. It should be put into the refrigerator as soon as cool.

Serve cold in a bed of parsley garnished with slices of lemon.