The sour rye soup is a soup made of soured rye flour and meat (usually boiled pork sausage or pieces of smoked sausage, bacon or ham). It is specific to Poland, where it is known as żur or żurek, and a variant is known as barszcz biały ("white barszcz") which is made with wheat flour instead of rye. The soup also occurs in the cuisines of other western Slavic nations such as Slovakia (kyslóvka) and the Czech Republic (kyselo). A variation of this soup is found in Lithuania.
In Poland it is sometimes served in an edible bowl made of bread or with boiled potatoes. The recipe varies from region to region.
In Silesia, a type of sour rye soup known as żur śląski is served in a bowl, poured over mashed potatoes. In the Podlaskie region, it is common to eat żurek with halved hard-boiled eggs.
In Poland żurek is traditionally eaten at Easter, but is also popular during other parts of the year. It is usually served with bread or buns, and sometimes flavored with bits of sausage.