The Deli-Style Potato Knish

Before you start

• Render your schmaltz ahead of time.

  If you are not buying jarred schmaltz, render chicken fat slowly over low heat with a few onion scraps until the fat runs clear and the cracklings are golden, straining it well before use.

Ingredients

• unbleached all purpose flour2 1/2 cup
• baking powder1 tsp
• Diamond Crystal kosher salt1 1/2 tsp
• egg1 large
• liquid schmaltz1/3 cup
• warm water1/2 cup
• distilled white vinegar1 tsp
• Yukon Gold potatoes3 lb
• schmaltz3 tbsp
• yellow onions2 large
• egg1 large
• Diamond Crystal kosher salt1 tbsp
• black pepper1 tsp
• egg1 large

Method

1. 01

   Melt the schmaltz to slowly caramelize the onions.

   Place a large, heavy-bottomed skillet over medium-low heat, melt the schmaltz, and add the diced onions with a heavy pinch of salt. Cook slowly, stirring occasionally, until they turn a deep, jammy brown—do not rush this 30 to 40 minute process.

2. 02

   Mix the dough until just smooth.

   In the bowl of a stand mixer, whisk the flour, baking powder, and salt. Create a well and pour in the warm water, beaten egg, liquid schmaltz, and white vinegar, then knead with a dough hook on medium-low for 3 to 5 minutes until soft and tacky.

3. 03

   Rest the dough for at least an hour to relax the gluten.

   Form the dough into a smooth ball, wrap it tightly in plastic wrap, and leave it at room temperature to ensure the vinegar and resting time can properly relax the gluten network for extreme stretching.

4. 04

   Boil and thoroughly drain the potatoes.

   Cover the cubed potatoes with cold, heavily salted water in a large pot, boil until completely tender, then drain and briefly toss them in the hot, empty pot off the heat to evaporate excess steam.

5. 05

   Mash the potatoes and bind the filling with the caramelized onions and egg.

   Roughly mash the warm potatoes to maintain a rustic texture, fold in the deeply caramelized onions, salt, and pepper, and once slightly cooled, vigorously stir in the beaten egg before letting the mixture cool to room temperature.

6. 06

   Stretch the rested dough until nearly translucent.

   Divide the dough in half and roll one piece on a lightly floured surface into a large 10-by-20-inch rectangle, stretching it as thin as possible until it is less than 1/8-inch thick.

7. 07

   Encase the filling tightly in a long dough log.

   Form half the cooled potato filling into a thick, uniform log along the bottom edge of the dough, lightly egg wash the top border, and roll the dough tightly up and over the filling like a jelly roll.

8. 08

   Portion the knishes using a gentle karate chop motion.

   Using the side of your hand, press down firmly on the log at 3-inch intervals to pinch the dough layers together and separate the filling without squeezing it out onto the counter.

9. 09

   Twist, tuck, and dimple each pastry to shape.

   Twist each indentation to reinforce the seal, cut through the twist, stand the piece upright on its cut end, tuck the dough inward to secure it, and press your thumb into the top center to create the signature deli dimple.

10. 10

    Bake until deeply golden brown and firm to the touch.

    Arrange the shaped knishes 2 inches apart on a parchment-lined sheet pan, brush generously with egg wash, and bake at 375°F for 35 to 45 minutes, letting them cool slightly before serving.

Notes

• Schmaltz is the non-negotiable heart of the flavor profile.

  Liquid gold rendered from chicken skin and fat provides a savory depth that vegetable oil simply cannot touch, adhering to the traditional kosher laws of the Jewish deli. If you must substitute, neutral oil will make a perfectly authentic, albeit less flavorful, pareve dough.

• The "karate chop" method dictates the authentic pastry texture.

  Rolling the filling inside a massive sheet of stretched dough creates delicate, overlapping layers of pastry. Chopping it with your hands pinches these layers together cleanly, a technique that has defined Lower East Side bakeries for over a century.