For classic knishes: 1 Caramelize onions: In a large skillet over medium heat, combine butter or schmaltz and olive oil. ... 2 Steam potatoes: Fill a large pot with 1" of water and place a steamer basket inside. ... 3 Carefully remove steamer basket and drain water from pot. ... More items...
Place knishes on prepared baking sheet and brush with egg and water mixture. Bake, turning pan halfway through, until golden, 45 to 50 minutes. Let cool at least half an hour before serving. Steam potatoes: Fill a large pot with 1" of water and place a steamer basket inside. Bring water to a boil, then add potatoes and cover with a lid.
Traditionally, a knish is round, not square, baked, not deep fried, and always made with homemade dough, not puff pastry. The filling can include caramelized onions or even chopped up meat (like leftover corned beef – yum!), but the main ingredient is potato.
Fried knish companies popped up, making square, golden yellow potato bricks that were more durable, and easy for street vendors to stack in their carts. (Hot tip: Most knish lovers will tell you a fried knish is not a real knish.)