My folks were raised in Polish and Ukrainian households in rural Saskatchewan, so perogies to me are about as ingrained in the food culture as a burger or hot dog. They also must be served with sour cream. That detail is non-negotiable. Bacon bits and onions are popular additions.
"Pierogi (pronounced /pɪˈroʊgi/ pi-roh-ghee), also known as varenyky, are filled dumplings of Eastern European origin. They are made by wrapping pockets of unleavened dough around a savory or sweet filling and cooking them in boiling water. These dumplings are popular in Slavic (Polish, Slovak, Ukrainian, Russian), Baltic (Latvian, Lithuanian) and other Eastern European cuisines (such as Romanian), where they are known under local names. Pierogi are especially associated with Poland, Ukraine, and Slovakia, where they are considered national dishes.
Pierogi are often semicircular, but triangular and rectangular ones are also found. Typical fillings include potato, sauerkraut, ground meat, cheese, and fruits. The dumplings may be served with a topping, such as melted butter, sour cream, or fried onion, or combinations of those ingredients"