Name: Śledź po kaszubsku: Kashubian Herring in Sweet-Sour Tomato Sauce
Prep time: 20 min
Cook time: 18 min
Total time: 188 min
Yield: 4 appetizer portions
Cuisine: Polish
Ingredients: 500 g ready-to-eat salted herring fillets, drained; 250 g yellow onion, thinly sliced; 30 ml rapeseed oil; 70 g tomato paste; 60 ml 5% apple cider vinegar; 80 ml water; 25 g granulated sugar; 2 bay leaves; 8 whole allspice berries; 6 whole cloves; 0.5 g ground black pepper; 200 g rye bread, 4 slices of about 50 g each

Kashubian-style herring pieces in sweet-sour tomato and onion sauce, with whole spices and rye bread.

Yield 4 appetizer portions

Servings 4, one small plate per person

Dish type Kashubian-style sweet-sour herring appetizer

Difficulty Easy

Ingredients ↓

About Kashubian herring

Śledź po kaszubsku: Kashubian Herring in Sweet-Sour Tomato Sauce

Śledź po kaszubsku is associated with Kashubian and Pomeranian fish cooking. Herring has long been prepared in different ways across the region, and recipes depend on household and product traditions. Culture.pl describes the sweet-sour version with fried onion and tomato sauce; another account notes tomato paste, cloves and allspice in a Christmas herring sauce.

The name also appears on a documented Pomeranian traditional product, “Hylyng” opiekany z cebulą. That preparation uses flour-coated herring fried in a pan and then covered with a briefly boiled vinegar-water-onion marinade. It is related, but differs from this contemporary tomato-sauce recipe. The ranked entry specifically describes herring in a sweet-sour onion, tomato-paste, oil and spice sauce, so this version follows that profile without presenting it as the only Kashubian formula.

Ready-to-eat salted herring brings a firm texture and concentrated savoury flavor. The gently cooked onions soften the sharp edges of vinegar, while tomato paste adds body and a deeper sweet-sour note. Cloves and allspice are potent; the measured amount gives the sauce a warm aroma without overwhelming the fish. Chilling the finished dish lets the sauce coat the herring and the flavors settle.

Tips for success

Buy herring labeled ready-to-eat and follow the package's refrigeration and after-opening instructions.
Taste a small piece before soaking. If it is very salty and the label permits, soak it in cold water in the refrigerator, changing the water once.
Cook the onion slowly until soft and translucent; deeply browning it can make the sauce taste bitter.
Cool the sauce completely before mixing it with the fish. The vinegar mixture is for flavor, not a safety treatment for raw fish.
Use a clean nonreactive glass or food-safe container, cover it and chill at or below 4 °C.
Keep the appetizer chilled until serving and return it to the refrigerator promptly.

Ingredients

Herring and sauce

500 g ready-to-eat salted herring fillets, drained
250 g yellow onion, thinly sliced
30 ml rapeseed oil
70 g tomato paste
60 ml 5% apple cider vinegar
80 ml water
25 g granulated sugar
2 bay leaves
8 whole allspice berries
6 whole cloves
0.5 g ground black pepper

To serve

200 g rye bread, 4 slices of about 50 g each

Method

Directions

Check and prepare the herring.Use commercially prepared herring labeled ready-to-eat, and keep it refrigerated. Follow the package directions. If a small taste is very salty and the label permits, soak the fillets in cold water in the refrigerator for 20–30 minutes, changing the water once. Taste again, drain and pat dry. Do not use raw fresh herring for this no-cook preparation.
Soften the onion.Heat the rapeseed oil in a 30 cm skillet over medium-low heat. Add the sliced onion and cook for 10–12 minutes, stirring occasionally, until soft and translucent without deep browning.
Make the sweet-sour sauce.Stir the tomato paste into the onion and cook for 1 minute. Add the vinegar, water, sugar, bay leaves, allspice, cloves and black pepper. Bring to a gentle simmer and cook for 3–4 minutes, stirring until the sugar dissolves. Remove from the heat and cool completely. Remove the bay leaves and whole spices if preferred.
Combine and chill.Cut the herring into bite-size pieces if needed. In a clean nonreactive covered dish, layer or gently fold the fish with the cooled sauce. Cover and refrigerate at or below 4 °C for at least 2 hours so the flavors blend. Do not leave it at room temperature while chilling.
Serve cold.Divide into four appetizer portions and serve each with 50 g rye bread. Keep chilled until serving and return leftovers to refrigeration promptly.

Troubleshooting

The herring is too saltyIf the package permits, soak it in cold refrigerated water for another 10–15 minutes, then drain and taste again.
The sauce tastes too sharpStir in a little more sugar, a few grams at a time, and chill before tasting again.
The sauce tastes bitterThe onion or tomato paste may have browned too much. Next time, keep the heat lower and stir regularly.
The fish seems dryFold it gently through the sauce and chill longer; avoid breaking it into very small pieces.

Nutrition per serving

Serving basisone-quarter of the recipe, about 125 g herring with sauce and 50 g rye bread
Caloriesabout 580 kcal
Carbohydratesabout 52 g
Proteinabout 23 g
Fatabout 31 g
Saturated fatabout 4 g
Fibreabout 5 g

These are rounded estimates using generic USDA data for pickled herring, sauce ingredients and rye bread. Salted herring varies substantially in sodium and fat by brand, salting and soaking. This is not a laboratory analysis; use package nutrition data for a closer estimate.

Allergens and food safety

Serving, storage and make-ahead: Serve about 125 g drained herring with sauce per person, alongside one slice of rye bread. This is a cold appetizer. Make it at least two hours before serving so it can chill and the flavors can blend.

Serving, storage and make-ahead: Keep the covered dish at or below 4 °C and do not leave it at room temperature for more than 2 hours. Refrigerate leftovers within 2 hours in a shallow covered container and use within 3–4 days, or sooner if the opened herring package specifies a shorter limit. Do not freeze the assembled dish; the herring and onion sauce can lose their texture.

Herring is a fish allergen. Rye bread contains gluten. Check the herring and bread labels for additional declared allergens and cross-contact warnings. Use commercially prepared herring labeled ready-to-eat, keep it refrigerated at or below 4 °C and follow the after-opening instructions. Vinegar is used for flavor and does not cook raw fish or control parasites. Keep the assembled appetizer chilled, discard it if it has been at room temperature for more than 2 hours, and refrigerate leftovers promptly.

Frequently asked questions

Is this the same as the registered “Hylyng” herring?

No. The Ministry-listed “Hylyng” is coated in flour, fried and covered with a vinegar-water-onion marinade. This recipe follows a contemporary tomato-onion sauce version described in regional food writing.

Do I need to soak the salted herring?

Not always. Taste a small piece first. Soak it under refrigeration only if it tastes very salty and the package directions allow it; change the water once and taste again.

Can I use raw fresh herring?

No. This recipe is a chilled, no-cook preparation and uses commercially prepared ready-to-eat salted herring. Vinegar does not make raw fish safe.