A recipe for fat may strike some as strange, but fat is one of the key flavor elements in food. French cuisine would be unrecognizable without cream and butter. Indian cuisine relies heavily on ghee (clarified butter). Chefs in Mediterranean countries turn habitually to olive oil, while those in Tibet always have yak butter on hand. The recipe here is for rendered chicken fat, which is widely used in Ashkenazi Jewish cuisine. (The Yiddish word for it—schmaltz—has taken on a whole other connotation in American English.)
As much as we love cream, butter, and olive oil, rendered fat is sometimes a better choice for use in a sauce or as a complement to meats because it does not distract from the flavor of the other ingredients. We use our Modernist schmaltz to enrich chicken sauce, salad dressing, and garlic, but it has innumerable applications—you can even use it to fry eggs!
Buy chicken skin from your butcher, or collect scraps of fat and skin from other chicken recipes in the freezer until you have enough to render. Note that the same technique can be used for any animal fat, including turkey, duck, or goose skin, and fatty trimmings from cuts of pork, veal, or beef.
– Adapted from Modernist Cuisine at Home