For those that haven't tried them, the frozen ones are usually quite adequate. Of course, they aren't like the one's grandma made (sometimes they are better). We have the Mrs T brand frozen pierogies here, they do come in a couple of different options depending on your local store. Think of them like the Czech version of ravioli. You can just boil them, or then brown them in butter, or make a sauce to cover them or a sauce to dip them in...
Makes a nice addition to your diet if you want to have a meatless day or whatever. Most aren't fully vegan, but have dairy or eggs and are suitable for vegetarian or at least meatless.
And then there are what we called pieroshki -- baked "hot pocket" sort of things. Really good too. Prune filling, or I make more of a cinnamon roll variation with orange marmalade, poppy seeds, and walnuts. Tastes like grandma's house even if not quite right it appeals to my memories.
https://en.wikipedia.org/wiki/Pirozhki