Dough and filling. Beyond that, interpretations vary wildly. There are round knishes, square knishes, tall knishes, flat knishes, oblong, ball-shaped, tube-shaped, knishes that look like miniature tarts or cupcakes, even bottomless, roll-style knishes that resemble cinnamon buns. The one rule seems to be that regardless of the way it’s shaped, a knish has to be able to fit in your hand.
Fillings are almost always savory. The classic is mashed potato, usually with some cooked onions mixed in. Other time-tested fillings are cabbage, ground meat, cooked onions, kasha, cheese and sauerkraut (and if you’re suddenly getting the feeling that knishes are of Eastern European origin, you win today’s four dollar prize). Nowadays of course knishes can have just about anything in them. Spinach, tofu, sweet potatoes, smoked salmon, mushrooms, liver and onions, tuna, tofu, broccoli, pastrami, turkey, corned beef, asparagus…and those are just the more conventional varieties. Realistically, anything that can go into a pasty, empanada or pocket pie can go into a knish. Sausage, curry, black beans and rice, you name it.
As for the dough, classically it’s rather lean and simple, on the order of a pasty dough. However knishes can also be made from laminated doughs like puff pastry or my personal favorite, brioche. Most are baked, but as I mentioned yesterday, they’re frequently deep fried. Some of the trendier modern knish makers even grill theirs. Does that go to far? Eh, maybe. I’m not sure a grilled ahi tuna and wasabi pocket pie with a ginger dipping sauce qualifies as a knish. But then I’m not one to judge, since one of my go-to fillings is ham and cheese. Neither, I’m pretty sure, would have found favor in Yonah Schimmel’s original Manhattan knishery. But then if the knish is anything, it’s a utility pie, adaptable to just about any circumstance. So if you feel like filling yours with bacalao, or butternut squash, sage and parmesan cheese, I say, more power to you.