Chewing the fats: delectations.

HOW to find if a cook is good? Simply look in the refrigerator. If the necessary cooking fats are there, all well and good. If not, forget it and him or her. Warn your friends, shake the dust from your feet, declare a general anathema.

Over 80 per cent of the best main dishes depend on the use of fats or oils. Obviously, deep-fried dishes, from beignets of brains to simple French fries, require fat. Shallow-fried dishes -- fried liver or fried eggs -- require fat. But roast dishes such as leg of pork need fat too. Even meats rich in their own fat such as duck, want some added fat to start off the roasting. Grilled fish, especially the drier fish, require lots of added oil. Even dry-grilled dishes, fish or meat cooked straight on a plancha or a Le Creuset - type grill with only salt, need to be anointed with some oil or fat just before serving. So do barbecued dishes. In fact, take back that 80 per cent. It's nearly 100 per cent, because even poached dishes need a final greasy accompaniment. Poached turbot needs its hollandaise, boiled bacon its parsley sauce with lots of butter.

So no fat, no cook. But your glimpse of the fridge tells you even more. Not only must there be fats but the right fats. The minimum for any half-decent conservative cook is six: clarified butter, goose or duck fat, pork fat, chicken fat, beef fat, and -- this last not in the fridge but in some dark cupboard -- olive oil. The sophisticated cook will have more: goose and duck fat, a game fat (e.g., pheasant), several different pork fats. These are all soft fats -- that is, fat that has been melted down on its own or boiled down in water. Good cooks will also have some of the solid originals. How on earth can you make proper puddings without beef suet?

The right fat for the dish is decided by two things, temperature and taste. French fries need to be cooked at a high temperature, so they need a fat with a high boiling point, which means beef fat or one of the more expensive oils. But if they are to taste right, there is no contest: it's beef fat. Dishes such as cassoulet and many from the southwest of France require goose or duck fat. Nothing else will do. It's a lie to call a stew of mutton, sausage, and beans without duck or goose fat a cassoulet.

Recipes from Calais to Dijon and from the north of Italy may well require butter, preferably clarified. You do know how to clarify it don't you? Excuse me? You . . . Oh, for goodness' sake, look it up in any one of the dozens of cookery books you have ostentatiously displayed on your shelves.

Recipes from Lyon to the Mediterranean are more likely to demand olive oil. You want two sorts. Forget the pretentious charades. Just find one with a strong taste and one with a lighter taste. Try several varieties of each to find the best. No, there are no shortcuts. You will have to learn to taste them for yourself. Chicken fat has fewer uses, but it is extremely good for frying chicken eggs and for frying bread and sauteing potatoes. Lamb fat is nearly useless. I used to know a cat called Mini who wasn't. He sat under the butcher's block in a halal butcher shop and when Mohammed shaved the fat off the mutton and let it fall to the floor, Mini obligingly and enthusiastically vacuumed it up. Pork fat has the widest use as a general frying agent. It is necessary too for pastry and for frying offal.

Last, the good cook has not only a variety of fats but lots of each. Fats can be re-used, but it is better not to do so too often. They pick up flavors, and even agents that remove contaminating flavors, such as ginger briefly fried in the fat, are not infallible. Of course fats should not be labeled. Color and smell are enough.

So there we are. Once again that's what good conservative cooking is like. No shortcuts, no easy options. Do it properly or not at all.

Tough? There is a compensation. The only way to maintain a good stock of fats is regularly to eat large joints of beef from a good-sized animal; lots of fat and full-flavored red pork, again from an adult; plump geese, pheasants, and ducks, and hens with a good deposit of fat around the legs and up the bottom. It's a pleasant enough duty.