Kanapka ze Śledziem

Herring reaches the Polish kitchen already cured, and the sandwich begins with undoing some of that cure. A salt herring is soaked overnight in cold water or milk until it sheds enough of its brine to taste of fish rather than salt, then it is filleted and either dressed in oil with onion or steeped in a vinegar marinade for a few days. Buttered dark rye goes down, the fillet is laid flat across it, raw onion goes over the top, and that is the kanapka: open-faced, cold, no second slice on top. The herring carries the whole thing, oily and savoury and faintly sour, and the bread and the butter and the onion are there to frame a fish that has already done most of the work in the barrel.

The butter on the rye is structural rather than a habit. A cured herring is an oily, briny fillet, and a cold film of butter on the bread seals the crumb so the fish oil and any marinade sit on top instead of soaking through to a sodden slice, while its sweetness softens the salt edge the soaking did not fully take out. Skip it and the rye goes greasy and damp under the fillet within minutes. Soak the herring too little and the sandwich reads as pure salt; soak it too long, or in too many changes of water, and it turns flabby and washed-out with nothing left to taste. The onion has to be raw and sharp, because a fish this rich needs the clean bite, and the bread wants a close, sour crumb with the body to hold a flat line under a heavy wet topping.

It eats cold and bracing, a plate of strong flavours that do not need heat. The smell is briny and oily with the raw sting of onion over it; the herring is silky and yielding, salt and sea and a sour lift from the vinegar or a round richness from the oil, the fat coating the tongue. The onion crunches sharp and clean against it, the butter carries a cool sweetness underneath, and the rye lands dense and faintly sour to anchor the whole bite. A turn of black pepper or a scatter of chive sharpens the top. There is nothing melted and nothing warm, just cured fish and cold butter on dark bread, the plainest reading of a fish Poland has built dozens of cold dishes around.

The kanapka is the everyday face of śledź, and the named preparations crowd in around it. Śledź w oleju dresses the fillet in oil with onion and sometimes allspice; śledź w śmietanie binds it in sour cream; śledź po kaszubsku, in the Kashubian style of the Baltic coast, leans on a sweet-sour tomato and onion dressing; śledź pod pierzynką, herring under a duvet, buries the fish under layered grated vegetables and is a Christmas salad rather than a sandwich. Rollmops wraps a marinated fillet around onion and pickle and pins it with a stick. The plain open kanapka is the one with the least done to it, the fish laid bare on buttered rye, and most of those richer dishes are a step or two away from it.

For all the dishes śledź spins off into, the kanapka holds to one plain claim: the cure is the cooking. Nothing on the plate is heated. The fish was made edible and savoury in salt and vinegar long before it reached the bread, and the butter, onion and rye are the cold frame Poland settled on to carry it.

The Fish of the Fast and the Baltic

Herring has no inventor in Poland, but its hold on the table is old and traceable, tied to two things at once: the Baltic on the country's northern edge and the Catholic fasting calendar. Salt herring was the cheap, keepable sea fish that could travel far inland in a barrel, and it became the standing protein of the meatless days the Church imposed across much of the medieval year. The great salting trade of the Baltic and North Sea, run through the Hanseatic ports, moved herring across Europe by the cartload, and Poland's own coast supplied it directly, which is why a fish from the sea ended up the everyday food of towns nowhere near it.

That fasting fish reaches its highest seat on Christmas Eve. Herring is one of the twelve traditional dishes of the Polish Wigilia, the meatless supper eaten before midnight, where it appears in oil and in cream and under its blanket of grated vegetables, the secular weekday kanapka and the holiday spread drawing on the same cured fillet. The cheap protein of the lean days the Church imposed is now the dish a Polish family puts out first on the supper of the year.

The coast wrote itself into the fish by name and by charter. Śledź po kaszubsku takes its name from the Kashubians, the Baltic-shore people of northern Poland, and the herring harbours of Pomerania were incorporated as towns precisely around this trade in the thirteenth century, Szczecin in 1243 and Kołobrzeg in 1255 among them. The fish that fed the inland fasts came up salted out of those ports, chief among them Gdańsk, chartered by the Pomeranian duke around 1257 and the great herring harbour of the medieval Polish Baltic.