How to Make Traditional Polish Pierogi Pierogi are probably the most popular Polish dish. Traditionally, these famous dumplings are filled with a mix of potatoes, farmer's cheese and onion. First of all: there is no such thing as "pierogis". Pierogi in Polish is plural itself, no need to make them plural in English. If you see "Pierogis" in the grocery store refrigerator, run! They are probably not real Polish pierogi. It can...