A use for leftovers isn't pie in the sky. It's a knish.
My husband has a theory: When you decide to buy a new car, everywhere you look, you see that particular model. I don't know if that's true, but I can say with confidence that once you make a few hundred pies, everything begins to look like a pie. And that is how I came to define a knish as a kinda-pie, a pastry wrapped around filling. In fact, I put empanadas, calzones and samosas in the same category. It's all pie to me. And every iteration is delicious.
The deeper my dive into pie -- using this new, expanded definition -- the more I've come to understand pie can be a way to use up extra food. What home cook doesn't appreciate a new and creative way to re-imagine those few ounces of leftover roast chicken, a meager bowl of last night's chickpeas, or the remaining blueberries languishing in the refrigerator? With flaky pastry, from pie dough to phyllo, puff pastry to strudel, tuck in those bits and bobs and feed the family one more time, in a new and re-imagined form.
A knish (the K is voiced: ka-nish) is a classic filled pastry. While potato knishes are most common, there are other fillings, too, and the internet shows a few versions of the pastry. When I decided to include a recipe in my new book, "When Pies Fly" (Grand Central Publishing, 2019), I searched through the cookbooks my grandmothers passed down to me -- a Hadassah collection that was a gift to my great-grandmother Agatha and "The New Settlement Cook Book," inscribed to Mary with love from Aunt Sophie of Yum-Yum Coffee Cake fame. But it was in Mary's recipe cards that I found inspiration and a version of the recipe printed here.
Mary was Lithuanian by birth, and I believe this method, and most particularly the dough, was a product of that upbringing. A knish recipe often calls for dough that is both dairy- and meat-free, avoiding butter or animal fat, and using oil instead, which permits a kosher household (where dairy and meat are not mixed) to stuff the pastry with either filling. The recipe card had the rough outlines of the dough with a potato filling; admittedly, I added some personal flourishes, such as fresh herbs and creme fraiche. My grandmother did not know from creme fraiche.
The dough, whisked with a fork, comes together quickly, and I've learned to love the kneading, feeling the dough turn silky smooth under my hands. A required one-hour rest for the dough allows plenty of time to stir together the filling, particularly if re-imagining last night's leftovers. Here, I've taken mashed potatoes, generously seasoned and studded with fresh chives. Whatever filling you choose, it must have a strong flavor to stand out when surrounded by dough, so use salt and pepper liberally, and then taste.
The dough is reminiscent of strudel dough, but is even more elastic. It can be pulled to size like strudel, but it's bouncy and resistant, so a rolling pin is easier. I mark off a 12-by-12-inch space on the counter using painters' or masking tape, so I can aim for the correct size and shape. It will seem as if the dough will not fill that space, but it will, and it will be whisper thin. There is no need to flour the counter; this oily dough will not stick. I place a log of filling near the edge of the square and roll it up like a fat cigar, pinching the edge to seal.
Shaping the knish is like forming sausage; use a sharp knife or scissors to snip the long cylinder into six even pieces. Shape the knish by lifting and pinching together the edges of the dough. I like to leave the tops open so the filling is exposed, but it's also possible to crimp the top closed. Be careful not to compact the potato filling too much, as it expands during baking and will either volcano out of the top or bust through the sides.
I love to bring these knishes to a party. They're surprising, light, crispy and satisfying. Easy to serve as a finger food, these knishes will put to rest any thoughts of the belly bombs that lurk in deli cases. Make a double recipe and stash some away for brunch or an afternoon snack. I have them ready for the upcoming holidays, perfect to take along for Rosh Hashanah lunch or for breaking the fast on Yom Kippur. Just tell the hosts you'll be bringing pie.