In Poland, these are called 'Russian pierogis' - a classic recipe for dumplings with potatoes and quark. The dough is soft but strong, so you can easily freeze the pierogis. Serve with melted butter and fried onions or with a dollop of soured cream.
If you made too many pierogis to eat in one day, you can simply freeze them. Place stuffed, uncooked pierogis on a generously floured cutting board, one by one (but not touching each other) and place in a freezer. After approximately one hour, when they are frozen, transfer pierogis into a freezer bag. To serve, drop frozen pierogis into a large pot of salted, gently boiling water and proceed with the last step of this recipe.