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I WAS a potter before I began to write about food, which may be why I like to cook with thermometers to hand. A kiln is, of course, simply an oven for pots, and to achieve a satisfactory firing you need to know its temperature. For an approximate reading, I used a thermocouple, and depended on small ceramic cones that bend at particular temperatures for greater accuracy. Fortunately, cooking is carried out at considerably lower temperatures than firing clay and so measuring them is easier.

A Victorian cook had to estimate the temperature of an oven simply by opening the door and letting the hot air reach her face. Incredibly, one cookery book of the time advised holding one's hand in the oven to gauge the temperature, counting to 40 for pies and white bread, and to 20 for cooking meat and beans. Though I'm all for touchy-feely cookery, there are times when both safety and greater precision than pleasurably flushed cheeks are called for.

Brick-lined bread ovens, which still survive in parts of Britain, sometimes had a look-and-tell pebble embedded in the floor to give a rough indication of temperature. When the oven had been heated by burning bundles of brushwood, the pebble changed colour. I've looked in vain for such a pebble in our Devon bread oven. So on the one smoky occasion I attempted to bake bread in it, I used the more common method of sprinkling a little flour over the oven floor to watch how quickly it changed colour.

Early oven thermometers date from the 1850s - they are considered highly collectable in America, where more have survived - and the first oven thermostat appeared in the 1920s. Today, an oven thermometer costs little more than a fiver and they are widely available in kitchenware shops.

A mercury-filled oven thermometer can be left in it all the time. Some dishes, such as baked souffles and sponge-cakes, require an exact temperature for a successful chemical reaction. If you cook on a range or continuous- burning stove, two oven thermometers are invaluable since the temperature of each oven can vary from base to top and front to back.

Thermometers for measuring the temperature of food itself fall into two groups: those for solids and those for liquids. The former are constructed with a metal-sheathed probe that is embedded in the food to produce a reading. It can be reassuring to have an accurate thermometer available when cooking a large and expensive joint of meat. If you wish, an oven- proof mercury-filled meat thermometer, fixed into the thickest part of the joint, can be left in place while the meat cooks.

Thanksgiving turkeys are sold in the States ready to cook and already equipped with a "Throw-away Turkey Timer". These small plastic temperature- activated sensors are a great boon for the inexperienced cook. When the turkey is properly cooked and the meat has reached 82C/180F and is safely edible, an impossible-to-miss red button pops out of the end of the sensor. "Turkey-timers" are also sold separately for using with other poultry. Since undercooked poultry is one of the main causes of food poisoning, I hope these inexpensive and foolproof sensors will soon be available here.

Waiting around while hot jam cools on the windowsill is a thing of the past once you've acquired a thermometer that measures the temperature of liquids. A good quality alcohol-filled thermometer should measure temperatures from the 50C (lukewarm) required for making yoghurt, to 140C for jam-making, and through all the stages of sugar boiling needed for making ice-cream, fudge and French butter- icing, right up to 200C , recommended for deep- fat frying. The temperature gauge is shown either by the meniscus along the glass tube or on a dial at the top, well clear of the hot liquid.

I wouldn't be without my veteran Brannan thermometer, which has seen me through countless seasons of jam-making. Measuring the temperature is, I find, a better test for a set, because the thermometer indicates immediately when this is reached and so the preserving pan can be removed from the heat straight away. This avoids overcooking and yields a fresher, livelier taste.

It's a good idea, when making jam, marma-lade and preserves, to tie one end of a piece of string to the top of the thermometer and the other to the handle of the pan. Then you can easily test the temperature both in the middle and at the edge of the mixture. If the thermometer has a pan- clip, do use it - watching the thermometer sink into a seething mass of bubbling marmalade never improves one's temper.

If the accuracy of your thermometer seems dubious, it can be checked by immersing it in boiling water and ensuring it reads 100C/212F. In some models, the dial can be rotated to adjust the reading. Wash thermometers by hand (not in a dishwasher) and try not to drop them. Treated with care, a high-quality cooking thermometer should last for a decade or more.


Serves 4

45g/112oz unsalted butter

2 tablespoons fine wholemeal breadcrumbs

1 clove garlic, peeled and crushed

walnut-size piece of peeled fresh ginger, grated

30g/1oz flour

150ml/5fl oz milk

12 teaspoon smooth Dijon mustard

14 teaspoon finely grated zest of orange

225g/8oz fresh crabmeat, separated into brown and white meat

4 large eggs, separated

salt and milled pepper

2-3 best quality anchovy fillets, drained of oil and chopped

12 teaspoon finely chopped fresh dill

2 extra egg whites

Melt the butter in a pan. Brush a little over the inside of 1.25 litre/2 pint souffle dish, dusting with the breadcrumbs and set aside.

Stir the garlic and ginger into the butter over moderate heat for one minute. Blend in the flour and cook, stirring all the time, until foamy. Gradually mix in the milk and cook until thick and smooth. Stir in the mustard, orange zest, brown crabmeat and yolks over moderate heat until the mixture has thickened.

Remove from the heat, season to taste and keep warm. Gently mix the white crabmeat with the anchovies and dill. (The preparation can be left at this stage for two to three hours. When ready to complete the dish, carefully reheat the brown crabmeat by stirring over low heat.)

Whisk all six egg whites with a pinch of salt until stiff. Gradually fold in the brown crab mixture. Spoon two-thirds of the mixture into the prepared souffle dish, sprinkle the white crabmeat on top and cover with the remaining souffle mixture. The uncooked souffle should come to within 1cm/12in of the rim of the dish.

Bake in an oven preheated to 220C/425F/ Gas 7 for 20-25 minutes, or until risen and golden-brown and set almost all the way through. Serve the souffle straight away, with a salad of rocket and watercress, or with freshly cooked, well drained spinach tossed with melted butter and coriander leaves.