Romanian-Style Potato and Sausage Soup

In Bucharest, Romania, at Bucataria Local Food, a restaurant owned by brothers Adrian and Gabriel Alexe, we tasted a broth containing aromatic vegetables, potatoes and a local smoked sausage called babic. The dish is one of countless types of borş, or soups made with the tangy, slightly fruity, almost effervescent, fermented-grain liquid that goes by the same name. Our adaptation calls for easy-to-source kielbasa, and to mimic the fermentation notes and tart taste of borş, we use a pale lager (a pilsner is our preference), with a tablespoon of cider vinegar stirred in at the very end.