Pierogi are Central and Eastern European dumplings: a simple dough of flour, egg, and water or milk, rolled thin, cut into rounds, filled, sealed, and boiled, then often pan-fried in butter afterward. They are a staple across Poland, Ukraine, Russia, and Lithuania, with recipes going back to at least the medieval period; the name comes from the Slavic root "pirog," meaning pie or pastry. Common savory fillings include mashed potato, farmer's cheese, sauerkraut, ground meat, or mushrooms; sweet versions are filled with fruit or sweetened cheese and served as a dessert. Savory pierogi are typically topped with sour cream, caramelized onion, or bacon, while sweet pierogi are finished with sugar or a fruit compote.