Chicken stock can begin with either a raw or cooked chicken carcass or trimmings. The flavour comes from the meat left on the bones, but the vital gelatin that adds the luxuriant mouthfeel to stews and sauces derives from cartilage and connective tissue. For a classic haute cuisine clear stock, you could start with raw carcasses and chicken wing tips, both of which should be available cheaply or even free from your butcher. However, starting with the leftovers from a family roast is probably a more practical solution for most home kitchens and produces just as useful a result.
Put the leftover meat and bones into a large pot, cover with cold water and bring gently up to the faintest simmer. After half an hour or so, add any and preferably all of the following: carrots, onions, leeks, turnips and celery, chopped roughly. Here you can be really thrifty because the trimmings you will generate are almost as valuable in stock as the vegetables themselves. Leaves, stems, trimmed-off ends, rooty stumps, skins and peelings can all be kept in the fridge or freezer until your next stock-making session. (A vegetable stock can be made in the same way, but will be richer if you roast the veg first.) Add a few peppercorns and a bay leaf too if you fancy, but avoid any other seasoning - particularly salt - as it will become unpleasantly concentrated as the stock simmers down.
After a couple of hours, strain off the liquid. The remaining veg and meat can be discarded if you're feeling flush, or topped back up with more water and perhaps a few more veg for remouillage - a second go - which produces a still worthwhile grade-two stock.
Cool the liquid in a covered dish in the fridge, preferably overnight, which will allow the fat to float to the surface and solidify, making it easier to lift off with a spoon (either throw it away or use it as delicious cooking fat). Then the stock is ready to use, although it can be gently reduced by another half if you want it thick and jellified. Either way, it will store in the fridge for a week or two; better still, freeze it. If you pour smallish quantities flat in Ziploc plastic bags, you will have "sheets" of frozen stock which defrost quickly and can be snapped into smaller portions. Or you can use ice trays.
Making stock at home, a little like bread-making, requires discipline, a mindset and a regime. Unlike bread-making, it's simple and effortless. And once you know you have stock in the freezer, it will transform the way you cook. A bag of veg, cheap because of a seasonal glut, or those mystery objects at the bottom of the organic veg box become amazing soups after a swift poaching in stock, a blitz in the blender and perhaps a dot of butter or cream. After grilling meat, chicken or fish, you can deglaze the pan with a splash of wine and a shard or cube of frozen stock to create an instant and sophisticated sauce. A proportion of stock in the cooking liquid of any stew, tagine, hotpot or casserole gives a remarkable extra depth of flavour, sometimes transforming quite unprepossessing cuts (no wonder restaurants love this stuff). But perhaps my favourite use is to make gravy for meat or sausages, by adding stock to the pan juices and then gussying it up with port and a couple of cubes of butter - and thickening with a little cornflour if that is your way.
All courtesy of that lovely Tim Hayward in the equally lovely Guardian.