During the communist era, milk bars could be found in every Polish city. These were canteen-style restaurants where workers could come and eat decent, inexpensive portions of simple food in a no-nonsense setting. Despite their popularity in the 1970s and 1980s, most of the milk bars died away as the Polish restaurant scene was rapidly modernized; however, the few that survived are now increasingly treasured as an important part of Poland's cultural heritage. U Stasi is well-known for its friendly service (something that milk bars traditionally lacked) while Bar Mleczny Górnik (Miners' Bar) is basic to the core in all ways except the food, which is consistently good and outrageously cheap.
You can translate "bar mleczny" as “milk bar,” but the name is misleading. These Communist-era canteens (we recommend the aptly named Bar Mleczny in Old Town) recall Poland’s shortage economy in the 1950s, when the government subsidized meals for workers. Much of the menu back then was dairy based, hence the name, but locals these days sober up at them with everything from goulash to borscht.