Zupa szczawiowa z jajkiem/Щи зеленые с яйцом/Sorrel and egg soup.
Slovaks have šťavelová/štiavová/šóšková polievka as well, but I haven't eat it yet personally. I call it šťavel, but there are also variants štiava or šóška.
Instead, my auntie once cooked šťavelový prívarok, because it's just weed in grandpa's garden. Why even buying it goddamnit?!
I remember I didn't like it though Šťavel is the best if you eat it raw, in my opinion