Potato Knishes

1 . Stage

Prepare the dough: Combine the flour, baking powder, and salt in the bowl of a food processor. Add the water, oil, egg, and vinegar and pulse until just combined. It will resemble a shaggy dough that no longer sticks to the side of the bowl. Transfer the dough to a large bowl and cover with a kitchen towel. Let rest for 1 hour at room temperature, or overnight in the refrigerator.

2 . Stage

Cook the onions: While the dough is resting, make the filling. Heat the olive oil in a medium skillet over medium heat. Add the onion and cook, stirring frequently, until they have browned and softened, 30 to 40 minutes. Remove from the heat and season with salt and pepper.

3 . Stage

Preheat the oven to 375°F. Line a large baking sheet with parchment paper.

4 . Stage

Cook the potatoes and assemble the filling: Meanwhile, cook the potatoes in a pot of salted boiling water until fork tender, approximately 15 to 20 minutes. Drain and transfer to a medium bowl. Add the cooked onions to the potatoes along with the butter. Mash with a potato masher or fork until smooth. Let cool.

5 . Stage

Roll the knishes: On a lightly floured surface, roll the dough into a very thin rectangular sheet (approximately 10 x 20 inches). Place a 2-inch wide log of the potato mixture running about an inch from the bottom of the dough. Roll the dough around the filling and into a log. Not too tight—it should roll around the filling 3 to 5 times. 

6 . Stage

Form the knishes: Use your finger to make 11 indents equally spaced down the log approximately 2 inches apart. Use a small knife to cut the log at these points, making 12 knishes. Pinch at one end to seal; this will be the bottom of the knish. Pinch and twist at the other end or leave open.

7 . Stage

Brush with egg wash and bake: Combine the whisked egg and water in a small bowl. Place the knishes on the prepared baking sheet evenly spaced apart, pinched-side down. Use a pastry brush to brush each knish with the egg wash. Bake until golden brown, 40 to 45 minutes. Serve with deli-style mustard. Store leftover knishes in a paper towel-lined airtight container for up to 5 days in the fridge or 3 months in the freezer. Reheat refrigerated knishes on a baking tray at 350°F for 10 to 15 minutes until warm. Love the recipe? Leave us stars below!