makes 1.8 litres/3pt
Preheat the oven to 230°C/450°F/Gas mark 8.
Put the beef bones, onion and carrots in a large shallow roasting pan. Roast in the oven, uncovered, for 30 minutes or until the bones are browned, turning occasionally.
Drain off any fat. Put the browned bones, onion and carrots in a large stockpot or heavy saucepan. Pour 150ml/5fl oz water into the roasting pan and swirl around the pan. Pour this liquid into the soup pot. Add the celery, tomato, parsnip, potatoes, peppercorns, parsley, bay leaf, salt, thyme and garlic. Pour in 2.8 litres/4 3⁄4pt water.
Bring the mixture to the boil, then skim off any cloudy scum from the surface. Reduce the heat, cover the pan and simmer gently for 5 hours, skimming off scum from time to time as necessary.
Carefully strain the stock through a fine-mesh sieve. Discard the meat, vegetables and seasonings. Leave the stock to cool completely, then skim off any fat from the surface and discard.
Store the stock in the refrigerator and use within 3 days, or divide into portions and freeze until needed.