Rosemary & Garlic Roast Leg of Lamb with Golden Roast Potatoes

Rosemary & Garlic Roast Leg of Lamb with Golden Roast Potatoes

This classic roast leg of lamb is the perfect recipe for spring celebrations. Cooked with rosemary and garlic, we served it with crispy potatoes, vibrant braised leeks, mint sauce and gravy.

Follow the temperature guide to cook the lamb to your preference. With larger joints of meat, they are more susceptible to carryover cooking. We therefore recommend removing your lamb from the oven up to 10 °C below your final desired temperature, to allow it to rise to your preferred doneness as it rests.


If using a bone-in leg of lamb, be careful when taking your temperatures that you don’t accidentally probe the bone as this will provide an inaccurate reading. 

Rare: 52°C

Medium: 60°C

Well done: 71°C

For the lamb
  • 1.35 kg boneless lamb shoulder, rolled and tied (225g per person)
  • 10 g salted butter
  • 3 sprigs fresh rosemary
  • 6 cloves garlic, thinly sliced
  • 120 ml white wine
  • Cornflour
  • 2 tbsp vegetable oil
  • Salt and pepper
For the potatoes
  • 2 lb red potatoes
  • 110 g lard or duck fat
  • Fresh thyme leaves
  • Rock salt
For the leeks
  • 3 large leeks
  • Splash of white wine
  • Low salt vegetable stock cube

Use your Thermapen to check the temperature of the lamb as it cooks, and to spot check it all over once it’s done to ensure it has come to temperature throughout. You can also use a leave-in thermometer, like our DOT Digital Oven Thermometer, if you would prefer to be alerted once your lamb is cooked.

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The method for the lamb
  • Remove the lamb from the fridge at least 20 minutes before cooking to bring to room temperature. Heat the oven to 190 °C / gas 5.
  • Score the meat with a sharp knife in a criss-cross pattern, roughly 15 times, across the top. Insert a slice of garlic and a few leaves of rosemary into each cross. Rub the lamb with the oil and seasoning.
  • Place into a roasting tray and cook for 20 minutes. Turn the heat down to 170 °C / gas 3, then cook until the temperature on your Thermapen reads 52 °C for rare, 60 °C for medium or 71 °C for well done (or up to 10 °C below this if you are allowing for carryover cooking). Remove the lamb from the oven and rest for at least 15 minutes.
The make the gravy
  • To make the gravy, remove the meat and deglaze the pan with white wine. Using a wooden spoon, make sure all the meat is removed from the pan, add a cup of water to help with this process. Now transfer all the contents of the pan through a sieve into a small saucepan.
  • Over a high heat, allow the juices to reduce and thicken, adding more wine and a good pinch of salt. Once reduced, add some pre-diluted cornflour to the pan and whisk through. This will thicken the sauce. Just before serving add the butter to help give the sauce a glaze.
Method for the potatoes
  • Preheat the oven to 220°C / gas 7. Wash, peel, and quarter the potatoes. Start by cooking the potatoes in cold water, this ensures they cook evenly. Place on the hob on a high heat and bring to the boil, then turn down the heat and simmer for 8-9 minutes, until softened at the edges.
  • Meanwhile, place the lard or goose fat in a large roasting tin and heat in the oven for 10 minutes, until shimmering hot.
  • Drain the potatoes and give them a shake to roughen up the edges. Carefully place the potatoes in the baking tray with the hot fat. Turn them over once to coat in the fat and then place in the oven.
  • Cook for 30-35 minutes, turning once or twice in the last 15 minutes of cooking, until golden brown and crispy. Remove from the roasting tin and serve topped with a sprinkling of rock salt and some fresh thyme leaves.
Method for the leeks
  • Cut the leeks into three even pieces, split down the middle and clean out any hidden soil. Gently heat the oil in a pan and add the leeks, turning them in the pan until all sides are browned.
  • Add a splash of wine and the cumin seeds. Add the stock and gently cook the leeks until thoroughly cooked through, roughly 30 minutes.
  • Once everything is ready, serve thick slices of the lamb with a generous serving of roast potatoes and a spoonful of leeks. Top with the gravy.
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" I love my Thermapen, it really helps me cook with confidence. As a caterer the health and safety of everyone you cook for is paramount, but that doesn't mean you have to compromise with your cooking. A simple reassuring check with the Thermapen throughout the process is all that's needed to allow you to enjoy, and confidently serve what you've made"
Laura Tulloch
Thermapen Chef & Caterer
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