Preheat oven to gas 6, 200ºC, fan 180ºC. Place 6 large chicken legs with meat, or a mixture of bone-in thighs, backs and legs, in a very large roasting dish.
Peel and chop 3 carrots, 2 brown onions and 4 sticks of celery. Add to the chicken in the roasting dish. Season liberally and roast for 1 hour, then remove.
Put the chicken, veg and juices in a pot. Add 3 peeled garlic cloves, 3 peppercorns, 2 bay leaves, 3 litres of cold water and bring to a boil.
Part cover the pot with the lid. Turn the heat down to a low simmer and cook for 2 hours - it should just be bubbling slowly. Don't stir, or it will become cloudy.
Remove from heat and scoop out the chicken pieces (save for sarnies or pies). Strain the remaining liquid through a fine sieve into a bowl. Discard the veg.
Skim the excess fat from the top of the stock and taste for seasoning. It can be kept in the fridge for three days or frozen in small containers. Makes around 2 1/2 litres of stock.
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