Wikipedia writes:
Pierogi ... (... also spelled perogi, pierogy, perogy, pierógi, pyrohy, pirogi, pyrogie, or pyrogy in English or other Slavic languages ...) are dumplings of unleavened dough – first boiled, at which point they can be served with melted butter or various toppings, or then fried with onions – traditionally stuffed with potato filling, sauerkraut, ground meat, cheese, or fruit.
Say I buy some frozen pierogi (pierogies, pirogen, perogies) at the grocery store, and I boil them according to the package instructions. These particular perogies are made of a pasta-like outer dough with a potato-and-cheese stuffing. Which blessing (b'rachah, bracha, beracha, brocho, berocho, berochoh) should I say before eating them, and which afterwards?