Knishes are the Jewish equivalent of a wonton or tortellini-that is, a tasty filling enclosed in pastry. My mother's knishes were pillowsoft and golden with a meltingly tender filling. Like many delicacies, they came about as a means of extending a precious ingredient-in this case, a sliver of meat, the last of the cheese, or some leftover spiced lentils or rice-into a delicious treat to feed an entire family. In short, this recipe conjures leftovers into the food of dreams!
There is a bit of effort involved here, but the great thing is that knishes freeze well and make wonderful party food so your efforts will be worthwhile. If you're planning ahead, make the potato filling the day before and chill it in the fridge.