1.Place bones in a large saucepan with onion, carrot, celery, leek, turnip, parsnip, parsley sprigs, thyme, bay leaves and peppercorns. Cover with water.
2.Bring to the boil over a high heat and remove any scum and fat that rises to the surface. Reduce heat to low. Cover and simmer for 2-3 hours, skimming surface. Add extra water, if necessary, to ensure bones are always covered. Season to taste.
3.Strain the stock through a fine sieve and cool. If time permits, chill overnight and then remove any fat solids from the surface. Reheat as required and serve hot, sprinkled with the extra parsley.