When you follow cookery writers over the course of their literary careers, you can be surprised to discover discrepancies in the advice they offer. They tell you to steam green beans in one book, and to boil them in the next. In Real Fast Food (1992), Nigel Slater writes: "I am convinced chicken tastes better, and is somehow juicier, when cooked on the bone"; in The 30-Minute Cook (1994), his line is: "A boned leg gives the juiciest grill." Surely it ought to be possible to give definitive advice?
One reason why cookery writers keep adapting their techniques is that they need constantly to come up with fresh recipes. But the desire to adapt is strong anyway. You get bored. You decide that you have arrived at the unimprovable way of making roast potatoes; and then you start to wonder whether the effort of heating the oil and turning the parboiled potatoes in it may be unnecessary, and whether simply pouring oil from the bottle on to the potatoes would produce just as good a result. You question whether the food science lore you have come to accept - such as that meat cooked on the bone is juicier - is invariably true.
I have written here about changing my mind on the matter of salt in the cooking water of dried beans. (You should leave out the salt, is my latest opinion.) Another subject on which I have to make a climbdown is chicken stock. On my shelves, I have one cookbook - Home Food by Richard Whittington - that suggests you simmer stock for eight hours, and another - How To Cook Better by Shaun Hill - that gives a timing of 40 minutes. Hill is unusual: most recipes state that the longer you cook stock, the better. But I have followed Michel Roux, who in his book Sauces asserts that the flavour of chicken stock grows dull with a cooking time of above two hours.
I may have been wrong. The flavour of the vegetables grows dull after long cooking, as it does in a soup; but I am not sure that there is deterioration in the flavour of the chicken. Simmering chicken bones very gently for between three and four hours maximises the conversion of collagen to gelatin, which sets the stock when chilled and gives it a richly unctuous quality. So that is what I do now; and I also add chopped vegetables half an hour before the end.
I think that I was wrong, too, about the nutritional qualities of stock. It is extraordinarily hard to find trustworthy information on the subject; in the end, I settled on Good Housekeeping magazine's statement that stock "has no food value apart from some minerals". But can that be right? What about the gelatin? I now find recipes that suggest a serving of stock contains roughly half of the recommended daily dose of protein for adults. Chicken soup is a panacea, legend has it. And legend is as reliable as any other nutritional guide.
Nicholas Clee's food blog is at http://nicholasclee.blogspot.com