The flavors of South Asia and Eastern Europe collide in these flavor-packed potato knishes. These handheld snacks pack a spiced potato and pea samosa filling into the flaky tender dough characteristic of knishes. The result is a tasty, savory hand pie with a golden, flaky crust that encapsulates a bold, spicy filling.
To make the dough: In a medium bowl or bowl of a stand mixer fitted with the dough hook, combine the flour, salt, and baking powder.
In a separate medium bowl, whisk together the water, butter, egg, and vinegar.
Add the wet ingredients to the dry ingredients and mix until a shiny dough forms, about 1 minute, scraping the sides of the bowl as needed.
Transfer the dough to a lightly floured surface and knead by hand until it's mostly smooth and becomes less sticky, about 1 to 2 minutes.
Transfer the dough back to the bowl and cover. Let it rest for 1 hour at room temperature or overnight in the refrigerator.
Preheat the oven to 350°F with a rack in the center position. Line a baking sheet with parchment. While the dough rests, make the filling.
To make the filling: Place the potatoes in a medium saucepan and cover with about 1" of cold water. Over medium heat, bring the water to a boil and then reduce to a simmer, cooking the potatoes until fork-tender, about 12 to 15 minutes of total cooking. While the potatoes cook, gather the remaining filling ingredients.
Once cooked, drain the potatoes and transfer them to a medium bowl. Use a fork to break the potatoes into a coarse mash.
In a large skillet over medium-low heat, melt the butter just until it starts to foam. Add the spices all at once and stir until fragrant, about 20 seconds.
Add the fresh ginger and stir until fragrant, another 20 seconds.
Add the water, onions, peas, and salt, and stir to combine. Cook, stirring occasionally, until the edges of the onions become translucent and most of the water evaporates, about 5 minutes.
Add the potatoes and stir to combine them with the other ingredients. Use a flexible spatula to mash any remaining large bits of potato against the bottom of the pan. Once the mixture is uniformly combined, transfer it to a bowl to cool slightly.
To assemble and bake the knishes: Uncover and divide the dough in half (about 3/4 cup or 179g per piece). Transfer 1 piece of dough to a lightly floured work surface; re-cover the remaining piece. Use a rolling pin to roll the dough into a roughly 15" x 9" rectangle. The dough will be very thin.
About 2" from the bottom of the dough rectangle, add half the filling mixture (about 1 1/4 cup or 270g) in a long strip down the entire length of the dough. Use your hands to pack the filling slightly into a 2"-wide log stretching from end to end. Compressing the filling makes the knishes easier to roll without the filling spilling out the ends.
Using a bench knife, lift the 2" strip of dough at the bottom of the rectangle off the work surface and over the filling; it’s OK if the dough tears a little. Continuing to use the bench knife to assist, roll the log over 2 to 3 more times, or until a 1 1/2" to 2" strip of dough remains along the top of the rectangle. Bring that dough over the log and pinch it to seal, forming a roughly 16" long log.
Use the bench knife to divide the log in half lengthwise into 2 roughly 8" long logs. Divide those logs in half to yield 4 roughly 4" long logs.
Working with one small log at a time, pinch to seal one end closed, pushing in any filling that begins to come out. Tightly squeezing the pinched seam, turn the log about 90° to twist and seal the pinched end closed. Turn the log so that the sealed end is on the work surface; the filling will settle somewhat. Gently pull the dough on the top toward the center to mostly cover the filling, leaving a 1/4" to 1/2" opening. Use the palm of your hand to gently press the knish down so that it widens to about 3" across and 1" tall. Use the bench knife to transfer the shaped knish to the baking sheet and repeat with the remaining 3 pieces.
Repeat this process (steps 14 to 18) with the remaining dough and filling to yield 8 knishes; arrange them evenly spaced on the baking sheet. Brush the knishes with egg wash.
Bake the knishes for 35 to 40 minutes, or until the dough is light golden brown in places and the internal temperature measures about 210°F. Remove the knishes from the oven and transfer to a rack to cool slightly before serving, about 5 to 10 minutes.
Storage information: Store leftover knishes in the refrigerator, covered, for up to 3 days. To reheat, place knishes on a wire rack set on a baking sheet, cover loosely with foil, and bake at 350°F for 20 minutes, or until warmed through.
The filling can be made up to 3 days ahead and stored, covered, in the refrigerator. Use straight from the refrigerator and proceed with the recipe as written.
