My latest New Statesman column concerns changing your mind about ways to cook. You decide on a method, but after practising it for a while you start -- partly out of boredom and partly out of curiosity -- to question whether it really is the only or best way of working.
In Don't Sweat the Aubergine, I followed Michel Roux's advice in recommending that you cook chicken stock for two hours. Longer cooking, I claimed, would cause the flavours to grow dull. But recently I have come to suspect that the dullness of flavour comes from overcooked vegetables, and not from the meat. Longer cooking extracts more collagen from the bones, converting it into gelatin and enriching the stock. Now I simmer stock, very gently, for three and a half to four hours, adding chopped vegetables just half an hour before the end.
At the weekend, I made a kind of double stock. I poached pig's trotters, for another dish. Covering them required quite a lot of liquid, which I reduced before using it to cover the bones of a roasted chicken. I simmered this stock for three and a half hours. It was Saturday evening, and I was too lazy to add vegetables.
The stock, chilled, became a firm jelly.
I am not sure how long you should keep stock. In a recent Observer column, Nigel Slater advised that you throw it out once it starts to weep -- in other words, once bits of the jelly liquefy. The Food Standards Agency tells you to consume stock within two days. But I must admit that I have used stock that has been in the fridge for a week, with no ill effects.