Apple leg of lamb with mustard, herbs and celeriac purée

Preparation

1. Preheat oven to 325°F.
2. Heat vegetable oil in an ovenproof casserole over medium-high heat.
3. Pat leg of lamb dry if necessary. Season all surfaces with salt and pepper.
4. When the oil is hot, sear the leg of lamb for about 2 minutes on each side until browned.
5. Meanwhile, whisk chicken broth with juice, apple cider vinegar and mustard.
6. Add the stock to the pot with the herbs, garlic and butter. Bring to the boil.
7. Cover and place in the oven for 2 hours 30 minutes. Turn the leg halfway through cooking.
8. When the time is up, remove the casserole from the oven.
9. Add apples and onion to casserole. Remove herb sprigs. Return to oven for 30-45 minutes, until lamb is tender.

Puree:

1. Meanwhile, place the celeriac and potato in a saucepan with enough water to cover. Season with salt.
2. Bring to the boil and cook for 15-18 minutes until tender.
3. Drain and return to saucepan with butter and milk to taste. Mashed potato to make a purée.
4. Adjust seasoning to taste.