Don't Sweat the Aubergine

should be 210°C; and so on. I must admit that I don’t know what the correct readings are. I don’t trust my own oven to give them.
    Put your thermometer on an oven rack and check the temperature. Now put a pan of steaming water below it. You’ll find that the reading goes down. But the steam will not cause the thermometer in a 200°C oven to descend to the temperature of boiling water (100°C). In my experience, the pointer will drop to about 160°C. I cannot expect steam in the oven significantly to slow the cooking of, say, a joint of meat; indeed, it might speed up the process, because it cooks more efficiently than does radiant heat. For this reason, steam does not, as many cookery writers imply, help to keep meat moist.
    Another popular way of trying to keep meat moist is by wrapping it in foil. Steam builds up inside the foil; again, the meat may emerge drier than it would have done if left uncovered.
    According to Harold McGee (
McGee on Food and Cooking
), foil deflects a good deal of heat energy that radiates from the oven walls, ceiling and floor. When I put a loose tent of foil around my thermometer, left it for half an hour, and took a reading, the reading was just as high in the foil as it had been outside it; but perhaps we’re talking about the kind of heat rather than the temperature. Foil does give protection to certain foods. Whole garlic cloves, for example, go dry and bitter very easily if placed naked in an oven; surrounded by foil, they become mild and tender ( see here ).
    Cookery books use such formulae as: ‘Put in a gas mark 3/160°C oven for an hour and a half.’ That’s because writers don’t have enough room to give, every time, instructions along these lines: ‘Put in a gas mark 3/160°C oven, but keep checking to see if the liquid is bubbling too fast or too slowly; if it’s bubbling too fast, and the liquid is reducing faster than the potatoes are cooking, turn down the heat; if there’s little activity in the dish, turn up the heat; you want a very gentle simmer to allow the potatoes to cook while the liquid slowly reduces and thickens’ (see Gratin dauphinois, here ); and, even if they did have the room, they think, with justification, that readers would find such qualifications offputting. Just give us an instruction that will work!
    I am sorry to tell you that there are very few dishes that you can just put in the oven and forget about, confident that they will take care of themselves in the time the recipe specifies. Please bear this warning in mind when you read the recipes in this book, or in any other books. My oven may be hotter or cooler than yours. My roasting pan or casserole or gratin dish may be thicker or wider, or made of a different material. The meat in my stew may take longer to tenderize than the meat your butcher sold you. These factors mean that oven settings and times that work for me may not work when you try them.
    It’s worse than that: settings and timings that work for me one week let me down the next. I put a gratin dauphinois into the oven at 190°C, leave it for an hour, and come back to find it still swimming in milky liquid. Next time, the same settings and utensils produce a dried-out concoction sitting underneath a burned crust. I have to turn down a stew to the lowest oven setting because it’s bubbling too vigorously; the next stew, in a 150°C oven, declines to show any activity at all.
    You haven’t failed if your food doesn’t behave in the way the recipe writer tells you it should. Everyone has to improvise. The oven setting is not the point; the point is the result you want to achieve. Don’t approach roasting with the notion that you have to start cooking your meat in a 200°C oven for 25 minutes; think about the browning reactions you want to generate . If 25 minutes in a 200°C oven achieves them for you, good. Don’t take it as a rule that you should cook a stew in a 140°C oven; the rule is that you want the stew just to blip a little as it simmers. Turn the oven up or down until you get the effect you want. Even then, you need to be watchful. A stew that blips gently after 30 minutes may be boiling furiously an hour later.
    Then, to add another layer of complication, there are fan ovens. I don’t have one, so I’ll quote Jenny Webb, who, as author of
The Fan Oven Book
, should be authoritative. Fan oven owners can set their ovens at 10 to 20 degrees Celsius lower than recipes advise, she told readers in