Also known as: Polish rye soup, Sour bread soup
Prepare a large jar (1 litre/33.8 ounces or larger) with a hermetic seal - just like those used for preserves. Place all of the ingredients inside and store away in a cupboard for a few days. Stir the mixture every day.
Day 4 or 5: open the jar. If any mold has formed - remove it. Strain. The liquid that remains is our zakwas.
To make żurek soup, we need 500ml (2 cups) of zakwas. If you have any left over - store it in a closed jar for up to 2 weeks in the fridge.
Boil 2 litres (0.5 gallon) of water. Add sausage to the boiling water, season with garlic pressed through the press.
Add the bay leaf, allspice, pepper and dried mushrooms. Reduce the heat and cook 15-20 minutes.
Remove the sausage from water and set aside. Drain our broth with a sieve. Put dried mushrooms aside.
Add zakwas to the broth. Season with marjoram, salt and pepper. Cook on low heat.
Hard boil the eggs. Leave them to cool, peel and cut into quarters. Cut the sausage into slices, and cut finely the mushrooms.
Pour żurek onto a soup plate. Add sausage pieces, chopped mushrooms and an egg quarter. Season with a tablespoon of sour cream.