For the Dough:

2½ cups all-purpose flour

1 teaspoon baking powder

1 teaspoon salt

½ cup vegetable oil

1 large egg

½ cup water

For the Filling:

2 pounds Yukon Gold potatoes, peeled and cubed

1 large yellow onion, finely chopped

2 tablespoons butter or olive oil

½ teaspoon salt

½ teaspoon black pepper

For Assembly:

1 large egg (for egg wash)

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Preheat the oven to 375°F (190°C) and line a baking sheet with parchment paper.
Make the Dough: In a large bowl, mix the flour, baking powder, and salt. In another bowl, whisk together the egg, oil, and water. Pour wet ingredients into dry and mix until a soft dough forms. Knead lightly until smooth, then cover and rest for 30 minutes.
Prepare the Filling: Boil potatoes in salted water until fork-tender, about 15 minutes. Drain, mash until smooth, and set aside. In a skillet, sauté onions in butter or oil until soft and golden. Stir onions into mashed potatoes, season with salt and pepper, and let cool slightly.
Assemble the Knishes: Divide dough in half. Roll one portion into a large rectangle about ¼ inch thick. Spread half of the potato filling along one long edge, leaving room at the ends. Roll into a log and seal ends. Repeat with remaining dough and filling.
Shape and Bake: Slice each log into 3-inch pieces, pinching the sides to seal. Place seam-side down on the baking sheet. Brush with beaten egg.
Bake for 35–40 minutes until golden brown and puffed. Let cool slightly before serving.
Enjoy warm with mustard, sour cream, or on their own.

Add mushrooms, spinach, or cheese to the filling for variation.

Sprinkle sesame or poppy seeds over the egg wash for extra flavor.

Use russet potatoes if Yukon Golds aren’t available.

Make them vegan by using olive oil instead of butter and a plant-based milk wash.

Freeze baked knishes up to 2 months; reheat at 375°F for 20 minutes.