If keeping the recipe kosher is not a concern, the oil can be substituted with schmaltz, which is rendered chicken fat and can be found in the meat section of your grocery store. Schmaltz lends both depth of flavor and flaky texture, but any neutral oil will work just fine. The knishes can be formed and frozen, unbaked, for up to 1 month in a single layer in an airtight container. To bake from frozen, brush the knishes with egg wash and increase the baking time to about 1 hour 15 minutes. When measuring flour, we spoon it into a dry measuring cup and level off excess. (Scooping directly from the bag compacts the flour, resulting in dry baked goods.)