Hungarian Potato Salad

A cold composed salad of the German-Austrian Heringssalat type, built entirely from cooked and cured components so it can be assembled without a fire. The hinge is the vinegar: a half cup of undiluted vinegar over two cups of potato is aggressive by modern taste, and how you handle it decides whether the dish is bracing or inedible.

• The vinegarVinegar of the period was broadly comparable in strength to modern table vinegar, and a half cup undiluted over two cups of potato makes for a sharply sour salad. Cut it with two or three tablespoons of oil, or use half vinegar and half of the herring's own pickling liquid, if you want it closer to current palates.
• Spiced herringThis means a whole salt-cured herring in spiced brine, sold from the barrel. Jarred pickled herring fillets in wine or spiced brine are the direct replacement; one fillet or two small ones stands in for the single fish. Rinse and pat dry if the brine is very salty.
• SardinesCanned oil-packed sardines. Drain them, but reserving a spoonful of the oil to add back is worth doing, since the recipe adds no fat of its own beyond what the fish and ham bring.
• Walnut picklePickled green walnuts, picked before the shell hardens and cured in spiced vinegar until black. Still made in Britain and sold in jars; sliced cornichons or pickled onions are the practical substitute if you cannot find them.
• PotatoesUse a waxy variety, boiled in their skins and peeled while warm so the slices hold. Warm potatoes take up the vinegar far better than cold ones, which is the usual trick in this family of salads.
• SaltNone is called for, and none is needed at first: herring, sardines and ham each bring their own. Taste after the salad has stood before adding any.
• Standing timeGive it at least an hour in the cold so the beet colours the potato and the acid softens the onion. It is better the next day, kept refrigerated.
• YieldTwo cups of potato plus the fish makes a substantial side for four, or a light main course for two.