Chicken stock means different things to different people. In this book, unless specified, it means chicken bones (or chicken boilers), slowly boiled in water with carrots, celery, onions and salt. The purpose of cooking slowly is to allow the fat and any impurities to come to the top without boiling back into the stock. This is then skimmed off during cooking.
Some salt must be introduced from the start for the flavour to develop properly. You can always add more if needed. On the other hand, if you add only at the end, as is often taught at various cooking schools, it will not taste right.
The stock must be clear, flavoursome and golden. Only then can you use it for things like risotto and soups. Cooked with small Italian pasta, it makes a great minestra – a dish virtually unknown outside Italian homes, but one of the ultimate comfort foods.