Put 1 kilo of lamb bone in a large heavy-based saucepan with 1 large carrot (quartered), 1 onion (quartered), half a celery stick (quartered), 1 bay leaf, 2 large sprigs of thyme, a generous sprig of parsley, 6 black peppercorns (crushed) and 1 tsp salt. Pour in 3 liters water. Bring to the boil and simmer uncovered for 2 hours.
Strain and return to the pot. Reduce until 1,3 liters of stock. When frozen you can keep this three months.