sour rye soup — Poland

Sour rye soup, known in Poland as żurek, is a tangy soup built on fermented rye flour, giving it a sour, faintly yeasty flavor sometimes compared to a paler, milder relative of borscht. The souring comes entirely from the fermentation of the rye starter, not from vinegar or lemon. It is reported throughout Poland, appearing in home kitchens and restaurants alike, and is closely tied to Easter meals, where it is often served in a hollowed-out bread bowl alongside boiled eggs and sausage. It is also eaten through the rest of the year as an everyday soup, particularly in colder months. A rye flour and water mixture is left to ferment for several days until it turns pleasantly sour, then this starter is added to a broth simmered with vegetables such as carrot, parsley root, celery and garlic, along with marjoram. The soup is finished with smoked bacon or sausage, and often topped with a halved hard-boiled egg; some cooks also stir in fresh horseradish for extra bite. Some cooks thicken the soup further with cream or a spoon of flour, others keep it thin and clear. The choice between bacon, sausage, or a meat-free version, and the amount of garlic and marjoram used, differ from one household to another, as does the length of time the rye starter is left to ferment.