Method:
Roughly chop the carrot, celery, onion and garlic and add to a large saucepan on a low heat
Cook the veg on a low heat for 1.5 to 2 hours stirring regularly, the veg needs to be very soft but have no moisture left in it
Pre heat the oven to 210 degrees, after the veg has been cooking for around an hour put the lamb bones in roasting tin and cook for 45minutes until they are golden
Remove the bones from the oven and carefully put them into the saucepan with the vegetables leaving the fat behind in the tin
Carefully tip the lamb fat from the bones into a heat proof bowl and reserve this for the potatoes