Polish Żurek is traditionally prepared for Easter. In some Polish families White Borsch is cooked instead of Żurek, the difference is Kvas/ sourdough that is used. For Żurek- rye sourdough, for Borsch – wheat sour starter.
Sourdough is a basic ingredient of Żurek, traditional Polish soup, prepared for Easter. It can be also called: kvas or sour starter, and is made by fermenting rye (for Żurek) or wheat (for White Borsch) flour. The process is easy, although you need few days to have your own homemade Sour starter.
There is a whole variety kinds of sourdough, that you can prepare and use for soups, it depends on the flour you use. I prefer oatmeal one, because you can get very fresh flour on the spot- all you need to do is to grind oatmeal in an old coffee mill:)