Schmaltz is rendered chicken fat look for it in the meat section of your grocery store. 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.)