Heat oil – or mutton dripping – in casserole dish on hob and seal the mutton on all sides until well caramelised. Add onion to soften in the juices.
Add liquid, loosening any delicious browned residue, rosemary sprig and seasoning. Cover and slow cook for 1½ hours at 170 °C. Check occasionally to ensure it remains moist, adding a little water as necessary.
Rinse the vegetables, cutting the peeled carrot and parsnip in chunks and slicing the leek.
Remove casserole from oven and add all the vegetables.
Return to oven for another hour. The mutton is ready when it falls from the bone. Taste and adjust seasoning.
I usually strip all the mutton off the bone and return the shredded mutton to dish.
It can then be served in heated bowls as a rustic soup or in a soup plate on a bed of buttery mash to sop up the wonderful juices.
You can also thicken the sauce further if you wish by adding a dessertspoon of blended cornflour. Stir and bring to the boil for a couple of minutes for the desired result.
Orkney Boreray is one of Scotland’s most rare sheep, reared only on Orkney and available through Macbeths when in season.