Slow roast lamb shoulder with pommes boulangère

Roasting a shoulder of lamb in a low oven for several hours gives you really tender, tasty meat, which is also easy to carve. At 150C, the oven won’t be hot enough for proper roast potatoes, but pommes boulangère – a dish of thinly sliced potatoes baked in stock – is perfect, as it can be left to cook in a low oven for a couple of hours or more while the lamb roasts to perfection. There’s no real gravy here, but rather a few spoonfuls of French-style jus made from some wine and either stock or water. Ask your butcher for some lamb bones and trimmings to use as a trivet, which will allow the heat to circulate the lamb and add flavour to the jus; mine didn’t have any so I sat the lamb on top of a few carrots and onions instead.

The story goes that in France, a dish of pommes boulangère – baker’s potatoes – would traditionally have been taken to the local baker to cook in the residual heat of his oven (many families would not have had an oven in their home). Anchovies aren’t traditional here, but they go brilliantly with lamb and add a meaty taste to the potatoes (they won’t taste fishy at all, I promise).

Serves four, or two with enough lamb left over for shepherd’s pie (see above).

For the lamb

Lamb shoulder (about 1.5 kg)

Rosemary, a bunch

Anchovy fillets in olive oil, 6

White or red wine, a glass of whatever you’re having with the lamb

Water or stock, 500ml (you may need more as I cooks)

Garlic, 1 whole head plus two extra cloves (I used new season’s garlic)

Olive oil (not extra virgin), or another light oil

Lamb bones and trimmings (or a few large carrots and an onion).

For the Pommes Boulangère

Potatoes, deseree are good, about 150g

1 small onion

Chicken stock,

Rosemary, a few sprigs

Anchovy fillets in olive oil, 6 (optional)

Garlic, 2 fat cloves

Anchovies, 4-6

Butter, about 20g

Set your oven to 210C (for a fan oven)

Score the fat that covers one side of the shoulder with a very sharp knife (or ask your butcher to do it for you when you buy the lamb).

Make some fairly deep incisions in the lamb with the point of a sharp knife and insert a sliver of garlic and half an anchovy into each.

Strip the leaves from one of the rosemary bunches, chop them roughly and pound them with some olive oil (from the anchovies if you like) in a mortar and pestle (if you don’t have one then just chop and bruise the rosemary with a knife and mix everything to a slush in a bowl).

Rub the rosemary slush all over the lamb and season the joint with plenty of pepper.

If you’re using the lamb bones, rub them with a small amount of olive oil, place them in a roasting tin and put it in the oven for about 10 minutes, or until the bones brown lightly. Meanwhile, boil the wine in a small saucepan for 30 seconds to remove any harsh flavours.

When the lamb bones are lightly browned take the roasting tin out of the oven. Split the head of garlic in half across and add both halves, cut side up, to the tin. Set the lamb in top and put everything back in the oven for 20 minutes.

Take the lamb out of the oven, and turn the heat down to 150C. Baste the lamb with any juices in the tin, and then pour in the wine and stock. Cover the lamb loosely with foil and return to the oven to roast for four hours, basting every hour or so.

While the lamb is cooking, peel and slice the potatoes (they should be about 2mm thick; it’s easy to do this in a food processor with a slicing attachment). Leave the potatoes to soak in cold water for up to an hour.

Peel the onion, cut it in half and then slice very thinly. Slice the garlic cloves.

Strip the leaves from the rosemary and chop most of them, leaving a few whole ones to sprinkle over the top. Chop the anchovies (if using) and mix them with the chopped rosemary (or pound the two together in a mortar and pestle).

Melt the butter in a small saucepan.

Scatter a layer of potatoes over the base of a baking dish and scatter a few onions, some chopped garlic and some of the anchovy-rosemary mixture on top.  

Continue in this way, seasoning each layer with pepper and drizzling with melted butter until all the potatoes are used up.

Mix the stock and milk together and pour over the potatoes (you want it to just reach the top layer).

Cover the dish with foil.

When the lamb is about half way through its cooking time, add the potatoes and cook for one and a half hours. Then take off the foil and allow to cook for a further hour uncovered.

When the lamb is cooked, remove it from the oven and spoon the clear fat from the top of the jus (there will be quite a lot). Pour the jus into a small saucepan and leave the lamb, loosely covered with foil to rest for 20 minutes. While you wait for the lamb to rest, turn the oven back up to 210 to brown the top layer of potatoes.

When everything’s ready, heat the jus, taste and season – if it’s too intensely meaty then add a little red currant jelly.

The shoulder is not the easiest cut of lamb to carve, but after slow cooking it should come easily away from to bone and there should be lots of crisp fatty bits, too.