FOR A LONG TIME, fat was a four-letter word (so to speak). Nutritionists and health-care workers preached about its many perceived evils, and a fat-free diet was seen as the ideal. Fortunately, more moderate minds have prevailed and fat is now generally accepted as an essential part of a healthy diet. There are many kinds of fats. Oils are liquid at room temperature and come from vegetables, nuts and fruit such as olives, peanuts, corn, coconut. Solid fats are liquid when heated but become firm at room temperature. Most of these come from animals but spoil quickly, so they are rendered (cooked slowly over a low heat), which separates the fat from the liquids and solid substances (such as connective tissues), which would otherwise cause the fats to spoil. Beef fat is made into suet and pork fat into lard. Other fats are made from chicken, geese and ducks. Butter is another animal fat made by churning cream to rid it of most of its moisture. Non-animal fats are made chemically and turn vegetable oils into solid substances. These hydrogenated vegetable shortenings and margarines were once seen as healthier than other fats, but now it is believed they're worse. Each type of fat has certain uses, and the qualities that make one the best for baking might make it unsuitable for deep-frying. Peanut, corn and canola oils are good for cooking because they have high smoke points and are fairly neutral in flavour. Extra-virgin olive oil is wonderful when used raw in salad dressings or drizzled over a dish at the last minute to add flavour, but it burns easily, and its elusive flavours are lost if the oil is heated. Many people believe even regular olive oils should never be used for cooking, although they're widely used in the Mediterranean. The expensive oils made from nuts and vegetables (such as hazelnuts, walnuts, pumpkinseeds and avocados) are also better used as a flavouring than a cooking medium. Lard - traditionally the fat of choice for Chinese cooks - is unfortunately still out of favour with the anti-fat brigade. It adds a lovely richness to savoury dishes and makes the flakiest pastry. To make your own lard, chop fresh pork fat into cubes and put them in a heavy-bottomed pan with a little water. Cook over a low heat until the fat renders out. Ladle off the clear fat as it rises to the surface and strain it into a sterilised jar or bowl. Fats made from poultry tend to be used less often in cooking except in areas where geese, ducks and chickens are raised commercially. Schmaltz - made by rendering chicken fat with chopped onions - is used in Jewish and Eastern European cuisines. Goose and duck fats are used frequently in French cuisine, especially for confit and rillettes.