Ingredients

Equipment Needed

• •Large roasting tin with a rack
• •Sharp carving knife and fork
• •Meat thermometer (optional, but useful)
• •Warm serving platter or wooden carving board

Instructions

1. 1

   Prepare the lamb

   Take the lamb out of the fridge a good hour before you plan to cook it. Cold meat in a hot oven tightens and resists. Room temperature meat relaxes into the heat. While it comes up to temperature, set your oven to 220C/200C fan. With a sharp knife, make deep incisions all over the leg, twenty or so, evenly spaced. Push a sliver of garlic and a few rosemary leaves into each cut. They'll disappear into the meat and scent it from the inside out. Rub the whole leg with olive oil, then be generous with salt and pepper. More salt than you think. The fat needs it.

   Ask your butcher to trim any excess fat but leave a good layer on top. That fat bastes the meat as it renders and crisps into something you'll fight over at the table.
2. 2

   Start it hot

   Put the lamb on a rack in a roasting tin, or directly in the tin if you haven't got a rack. Into the hot oven for twenty minutes. This initial blast of heat does two things: it starts rendering the fat and it begins to build a crust on the outside that will turn golden and sticky and smell like the reason you invited people for lunch. After twenty minutes, turn the oven down to 180C/160C fan.

3. 3

   Roast to your liking

   For pink lamb, which is how I like it and how I think it wants to be eaten, cook for about twenty minutes per 500g at the lower temperature, plus twenty minutes for the initial blast. For a 2.5kg leg, that's roughly an hour and twenty minutes total. For well done, add another fifteen to twenty minutes per 500g. But honestly, lamb roasted past pink loses something. The meat goes from yielding and blushed to grey and dry, and no amount of gravy will bring it back. Trust your instincts. Press the meat with your finger: soft and springy means rare, firmer but still giving means medium. If it feels like the heel of your hand, you've gone too far.

   If you have a meat thermometer, 55-58C in the thickest part gives you pink. But a thermometer is a guide, not a guarantee. Every oven lies. Every joint is different. Press the meat. Look at the juices. Your senses will tell you more than a number.
4. 4

   Rest the lamb

   This is the step people skip, and it's the one that matters most. Take the lamb out of the oven, transfer it to a warm platter or board, and cover it loosely with foil. Let it rest for at least twenty minutes, thirty is better. The meat relaxes. The juices, which have been driven to the centre by the heat, redistribute through the whole joint. A rested leg of lamb carves cleanly and gives you slices that are evenly pink, juicy, and tender. A leg carved straight from the oven bleeds all over the board and the meat clenches. Patience here is the difference between good and wonderful.

   Don't worry about it going cold. A 2.5kg joint holds its heat like a small radiator. Thirty minutes under foil and it will still be properly warm when you carve.
5. 5

   Make the mint sauce

   While the lamb rests, make the mint sauce. Pile the chopped mint leaves on a board, scatter the sugar over them, and chop them together until the sugar dissolves into the mint and everything turns dark green and fragrant. Scrape this into a small bowl or jug. Add the vinegar and a tablespoon or two of boiling water. Stir. Taste it. The balance should be sharp, sweet, and fresh, each quality pulling against the others. Adjust with more sugar or vinegar until it's right. This is nothing like the stuff from a jar. The first time you make it, you'll wonder why you ever bought it.

6. 6

   Cook the new potatoes

   Put the new potatoes in a pan of well-salted water. Bring to the boil and cook until a knife slips through without resistance, about fifteen to twenty minutes depending on their size. Drain them, return to the pan, and toss with butter and a pinch of salt. They should be glossy and steaming and smell of the earth they came from. If you can get Jersey Royals, this is their moment.

7. 7

   Make a simple gravy

   While the potatoes cook, set the roasting tin over a medium heat on the hob. Pour off most of the fat, leaving the sticky, dark residue on the bottom. This is where the flavour lives. Pour in a glass of white wine or water and scrape up all those caramelised bits with a wooden spoon. Let it bubble and reduce by half. It won't be a thick gravy. It's more of a savoury juice, thin and intense, which is all a good piece of lamb really needs. Season and strain into a warm jug.

8. 8

   Carve and serve

   Carve the lamb at the table if you can. There's something about bringing the whole joint to the board in front of people that turns dinner into an occasion. Cut along the bone, then across the grain in thick slices. The inside should be pink and yielding, the fat golden and crisp. Serve with the buttered new potatoes, the mint sauce in a jug so people can help themselves, and the gravy alongside. There are few better feelings than putting this plate in front of someone on a spring Sunday.

Chef Tips

• •Buy the best lamb you can afford. British lamb, from a butcher who can tell you where it came from, will taste like the hillside it grazed on. Supermarket lamb will give you dinner, but it won't give you that. This is not the place to economize.
• •Bring the meat to room temperature before roasting. A cold joint straight from the fridge will seize in the heat and cook unevenly, rare in the middle and overdone at the edges. An hour on the counter solves this.
• •Rest it longer than you think. Twenty minutes is minimum. Thirty is better. The resting is where a roast becomes itself. Skip it and you lose half the juice to the cutting board.
• •The mint sauce improves if you make it twenty minutes before serving and let it sit. The sugar softens the vinegar, the mint releases its oils, and the whole thing settles into something balanced and alive.
• •Save the bone. A lamb bone simmered with an onion, a carrot, a stick of celery, and cold water for three or four hours makes a stock that will carry you through a week of soups and braises. It freezes beautifully.

Advance Preparation

• •The lamb can be studded with garlic and rosemary up to a day ahead. Cover and refrigerate, then bring to room temperature for an hour before roasting.
• •Mint sauce can be made an hour or two in advance and left to sit at room temperature. It actually benefits from the wait.
• •New potatoes can be scrubbed and halved ahead of time, kept in cold water until ready to cook.

Frequently Asked Questions

Nutrition Information

1 serving (about 420g)