Żur kujawskiKuyavian sour rye soup

• 100 g3/4 cup rye flour (mąka żytnia), wholemeal or light, for the Kuyavian starter (zakwas kujawski)
• 750 ml3 cups lukewarm boiled water, for the starter
• 3 garlic cloves, for the starter, halved
• 1 crust of rye bread, for the starter, to speed fermentation
• 1.2 l5 cups water, or, for a holiday żur, the broth from cooking a smoked ham
• 300 g10 oz Polish sausage, smoked or white (biała kiełbasa), whole; optional, see notes
• 100 g3.5 oz smoked bacon (boczek) or pork fat (słonina), finely diced; or 2 tbsp lard (smalec)
• 1 onion, finely chopped
• 150 ml2/3 cup sour cream (śmietana) or creamy whole milk
• 1 tsp dried marjoram
• salt and black pepper, to taste
• 800 g1.8 lb potatoes, peeled, boiled in salted water, to serve
• 4 eggs, hard-boiled, halved; for the Easter version

Method

1. 1

   1. Three to five days ahead, whisk the rye flour into the lukewarm water in an earthenware crock or a large jar, add the garlic and the bread crust, and cover with a cloth.

2. 2

   2. Leave it in a warm place, stirring once a day with a wooden spoon, until it smells sharply sour and separates into a clear top layer over a thick, grey flour layer; it is then ready, and keeps in the fridge for a week.

3. 3

   3. Bring the water or ham broth to the boil in a pot; if using sausage, put it in whole and simmer for 20 minutes, then lift it out and slice it.

4. 4

   4. Fry the bacon or pork fat in a pan over medium heat until the fat runs and the pieces turn golden, then add the onion and fry until golden brown, about 8 minutes. This is the okrasa (fat garnish).

5. 5

   5. Remove the bread crust and garlic from the starter and stir it well so the flour layer is fully mixed in.

6. 6

   6. Pour the starter into the boiling liquid in a thin stream, whisking constantly so no lumps form.

7. 7

   7. Simmer, stirring often, for 10 to 15 minutes, until the soup is thick, creamy-grey and opaque and no longer tastes of raw flour.

8. 8

   8. Stir in the okrasa of bacon and onion with all its fat, the marjoram, pepper and salt to taste.

9. 9

   9. Temper the sour cream or milk by mixing it with a ladle of hot soup, then stir it into the pot and heat without boiling.

10. 10

    10. Return the sliced sausage to the soup.

11. 11

    11. Serve hot, ladled over boiled potatoes in deep plates or with the potatoes alongside; at Easter add halved hard-boiled eggs.