This is a very popular soup in Poland, and especially on Easter. During Lent is can be seen without meat.
The magic soup roux is fermented like sour dough starter kinda. I just started some, so I took pics.
Add pictured stuff with 1/2 cup rye flour and 2 cups of water and set in a warm place for a few days, add another 1/2 cup flour and cup water and wait for 7 days total. Good idea to mix it up every day.
[Linked Image from i.imgur.com]
[Linked Image from i.imgur.com]
About 10 peppercorns, and about 10 all spice, maybe 5 bay leaves, 1 tbs majoreum leaves. Few crushed whole garlic.
Soup base is made with water, kielbasa, or maybe bacon slab, whole carrot, parsnip, celery or celery root. That all gets boiled, then the roux is added and again simmered. It will be thick.
Usually most slice up the carrot and meat and leave that in the soup. Other roots can be added or reserved for a salad. Served with 1/2 hard boiled egg, and usually everyone adds some horseradish when served. Very popular, and like many soups amounts and substitutions like being vegetarian is standard. The bottled fermented mix is sold in stores in Poland, so that is a shortcut. You can also get it as a dried soup mix on Amazon in foil packs and add fresh items. Roux is easy to make though. Plenty of versions on youtube. Classic soup this time of year, it is a spring celebration soup.