Polish Pickled Herring in Oil

Step 1

Remove the salt-cured herring fillets from their packaging and rinse them thoroughly under cold running water for about 2 minutes, rubbing gently with your fingers to remove the excess salt coating. You should see the water running clear and the fillets should feel less slippery.

Step 2

Place the rinsed herring fillets in a medium bowl and cover completely with 2 cups of cold water. Let them soak for 30 minutes to 1 hour — this rehydrates the fish and removes the remaining salt. You can taste a small piece after 30 minutes; if it still tastes quite salty, continue soaking.

Step 3

Drain the herring fillets in a fine-mesh strainer and pat them completely dry with paper towels. Examine each fillet for any remaining small bones or scales, and remove them with tweezers if necessary.

Step 4

Cut the large yellow onion in half from root to tip, then peel away the papery skin. Lay each half flat on your cutting board and slice crosswise into half-moon rings about 1/4 inch thick — you should have roughly 2 cups of onion rings.

Step 5

Choose a clean glass jar with a tight-fitting lid (a 1-quart mason jar works perfectly). This is your preservation vessel, and glass is essential because it won't react with the vinegar and oil.

Step 6

In a small bowl, combine 1 tablespoon of black peppercorns, 0.5 tablespoon of whole allspice berries, and 0.5 teaspoon of whole mustard seeds. Do not crush them — leave them whole so they perfume the oil gently rather than making it bitter.

Step 7

Begin layering in the jar: start with a thin layer of the onion rings (about 1/4 of your total), then arrange some herring fillets on top, then scatter a small pinch of the spice mixture. Repeat this sequence until all ingredients are used, finishing with a final layer of onion rings on top.

Step 8

Pour 0.75 cup of distilled white vinegar evenly over all the layers — you should see it seeping down between the fish and onions. The acidity is crucial for preservation and flavor.

Step 9

Pour 1 cup of extra-virgin olive oil over the vinegar until everything is completely submerged — the oil creates a protective seal and adds richness. Tuck 3 bay leaves and 2 fresh dill sprigs among the layers so they're visible through the glass.

Step 10

Sprinkle 0.5 teaspoon of kosher salt over the top. Seal the jar tightly with its lid.

Step 11

Refrigerate immediately. The herring will be palatable after 24 hours, but the flavors develop beautifully over 3-5 days as the vinegar and spices infuse. It keeps for up to 3 weeks in the refrigerator — the oil and vinegar preserve the fish indefinitely, but eat it within this window for best texture.

Step 12

To serve, use a clean fork to lift herring fillets and onion rings directly from the jar onto a small plate or bread. You can drizzle a spoonful of the pickling liquid over the top. Śledź w oleju is traditionally eaten as an appetizer on dark rye bread with a dollop of sour cream and fresh dill, or alongside boiled potatoes.