Put the carcass and giblets in water to cover. Bring to the boil. Skim. Add all the other ingredients. Add 2 litres (4 pints) of water and bring to the boil. Simmer VERY gently for 3 to 4 hours skimming regularly and adding more water if needed.
Strain through a fine sieve lined with muslin. Leave to settle then skim off the last traces of fat with kitchen paper. Return to the heat and reduce to 600 mls (1 pint). To freeze, reduce the stock down to a sticky consistency then pour into ice cube molds. These can be added to recipes at a later date by melting and adding more water.