Schmaltz rendered from a chicken or goose is popular in Jewish cuisine; it was used by Northwestern and Eastern European Jews who were forbidden by kashrut (Jewish dietary laws) to fry their meats in butter or lard, the common forms of cooking fat in Europe, and who could not obtain the kinds of cooking oils, such as olive oil and sesame oil, that they had used in the Middle East and around the Mediterranean (as in Spain and Italy). (The overfeeding of geese to produce more fat per bird produced postclassical Europe's first foie gras as a side effect.)
The manufacture of schmaltz involves cutting the fatty tissues of a bird (chicken or goose) or pig into small pieces, melting the fat, and collecting the drippings. Schmaltz may be prepared by a dry process where the pieces are cooked under low heat and stirred, gradually yielding their fat. A wet process also exists whereby the fat is melted by direct steam injection. The rendered schmaltz is then filtered and clarified.
Homemade Jewish-style schmaltz is made by cutting chicken or goose fat into small pieces and melting in a pan over low-to-moderate heat, generally with onions. After the majority of the fat has been extracted, the melted fat is strained through a cheesecloth into a storage container. The remaining dark brown, crispy bits of skin and onion are known in Yiddish as gribenes.
Since the rendering process removes water and proteins from the fat, schmaltz does not spoil easily. It can even be used to preserve cooked meats if stored in an airtight container in a cool, dry location. This is similar to the French confit.
Schmaltz often has a strong aroma, and therefore is often used for hearty recipes such as stews or roasts. It is also used as a bread spread, where it is sometimes also salted, and generally this is done on whole-grain breads which have a strong flavor of their own.