Roasted Leg of Lamb with Mint Sauce

Mark your next special occasion with my Roasted Leg of Lamb with Mint Sauce recipe! This one pan meal pairs tender and flavourful leg of lamb, perfectly roasted fingerling potatoes and a refreshing and vibrant mint sauce to create a swoon-worthy meal. This bone-in leg of lamb is quite the showstopper and is sure to impress all your guests. It’s so delicious that it will leave everyone wanting a second helping!

My Roasted Leg of Lamb recipe starts off with a large, bone-in leg of lamb from New Zealand. Lamb from New Zealand is revered for its more pronounced “lamb” or gamey flavour, which is due in part to its grass-fed diet. I love using bone-in leg of lamb for this recipe given its rich flavour. The bone serves as an insulator for the meat, yielding a slightly longer cook time relative to the boneless variety, and imparts a ton of flavour and richness into the meat. New Zealand lamb is regarded as being leaner relative to its American counterpart, however, its protective layer of fat keeps the meat incredibly juicy and tender when roasted. To give the lamb an additional flavour boost, it is coated in a fragrant herb, lemon and mustard rub, giving this dish some added brightness, freshness, sweetness and richness.

Roasting the leg of lamb is as much of a science as a work of art! The leg of lamb is placed into a baking pan or roaster, transferred to the oven and cooked at a high temperature, or 425°F, for the first 20 minutes of cook time. This cooking method allows the herb, lemon and mustard rub to slightly caramelize, forming the most beautiful, flavourful and fragrant crust. Lemon-infused fingerling potatoes are added to the baking dish, nestled amongst the leg of lamb, and the oven temperature is lowered to 350°F for the remainder of the cook time. We are cooking the lamb low and slow here! The lower temperature promotes a more even cook, ensuring that the leg of lamb stays juicy and tender. When cooking bone-in leg of lamb, the general rule of thumb is a cook time of 20 – 30 minutes per pound, depending on your desired level of doneness. For medium - rare, a cook time of 1 hour and 10 minutes will help you achieve lamb that is pink and moist. While a cook time of 1 hour and 30 minutes will yield lamb that is well-done or fully cooked without any pink colour remaining.

For perfectly roasted bone-in leg of lamb, follow my lamb cooking table below.

Level of Doneness *	Internal Temperature (in °F)	Internal Temperature (in °C)
Medium - Rare	145°F	63°C
Medium	160°F	71°C
Medium - Well	165°F	74°C
Well Done	170°F	77°C

* This table represents my cooking level and temperature estimates, using a gas oven.

Once cooked, resting the lamb for at least 15 minutes is crucial! This will redistribute and lock in the juices, keeping the lamb flavourful, juicy and moist once sliced. During this time, the lamb will also continue to cook (often referred to as carryover cooking), and the internal temperature of the meat will rise from anywhere between 5°F – 10°F. Therefore, when testing for the internal doneness of the meat, you will want to remove the lamb from the oven just shy of 5°F – 10°F from your desired internal temperature.

The roasted lamb is then cut against the grain into desired slices and served alongside melt-in-your-mouth, fork-tender potatoes. Drizzle with pan juices and top with a dollop of fresh and vibrant mint sauce. Mint sauce and lamb go hand in hand! You simply can’t have one without the other! Forget the store-bought sauce or jelly and make my homemade mint sauce instead. It’s so delicious, comes together quickly and is made using fresh mint, a shallot, extra virgin olive oil, red wine vinegar, honey, salt and pepper – that’s it! It pairs perfectly with the lamb and adds plenty of acidity, brightness, freshness, tanginess and spice to this indulgent dish.

Treat yourself to my Roasted Leg of Lamb after a long and busy work week or make it for your next celebratory occasion, such as Mother’s Day, Father’s Day, Christmas or Easter. It couldn’t be easier to make, comes together in just over 1 hour and 30 minutes and uses a handful of simple and everyday ingredients. So, let me show you how it’s done. Grab a spoon and come and cook with me!

For more fun and exciting celebratory meal ideas, try my Perfectly Roasted Turkey, Baked Salmon with Citrus and Fennel and Apricot Glazed Ham recipes!

Prep Time: 10 minutes

Cook Time: 90 – 110 minutes

Total Time: 115 – 135 minutes (includes 15 minutes for resting)

Serves: 6 – 8

Ingredients:

Leg of Lamb

• 5 lbs bone-in, New Zealand leg of lamb (approx. 2.354kg) (See Notes below)

• 1 ½ tsp kosher salt

• ½ tsp freshly ground pepper

Herb, Lemon and Mustard Rub

• ¼ cup extra virgin olive oil

• 4 garlic cloves, peeled and finely chopped

• 2 ½ Tbsp freshly squeezed lemon juice (juice of ½ large lemon)

• 2 Tbsp Dijon mustard

• 1 Tbsp honey

• 1 Tbsp fresh rosemary, finely chopped (approx. 2 sprigs of rosemary)

• 1 Tbsp fresh thyme leaves, finely chopped (approx. 6 - 8 sprigs of thyme)

• 1 ½ tsp lemon zest (zest of 1 large lemon)

• 1 tsp dried oregano

Roasted Potatoes

• 2 lbs fingerling potatoes, washed and dried

• 2 ½ Tbsp freshly squeezed lemon juice (juice of ½ large lemon)

• 2 Tbsp extra virgin olive oil

• 1 tsp garlic powder

• ½ tsp kosher salt

Mint Sauce

• 1/4 cup fresh mint leaves, finely chopped

• 1 shallot, peeled and finely chopped

• 2 Tbsp red wine vinegar

• 1 ½ Tbsp extra virgin olive oil

• ½ Tbsp honey

• ¼ tsp kosher salt

• Freshly ground pepper, to taste 

Instructions:

1. Preparing the Leg of Lamb: Remove the leg of lamb from the refrigerator and allow it to come to room temperature for at least 30 minutes prior to cooking. Using a sharp paring knife, trim off the fell (or silver skin) and discard.

2. Preheat the oven to 425°F and set aside a 9” x 13” ceramic baking dish or roaster, with a 4L capacity.

3. Pat the lamb dry with a paper towel and place it into the baking dish or roaster. Season with 1 ½ tsp salt and ½ tsp ground pepper and set aside.

4. Creating the Herb, Lemon and Mustard Rub: To a medium bowl, add ¼ cup olive oil, garlic, 2 ½ Tbsp lemon juice, mustard, 1 Tbsp honey, rosemary, thyme, lemon zest and dried oregano. Whisk until fully incorporated. Spoon the marinade over the top of the leg of lamb, ensuring that it is evenly coated.

5. Transfer the lamb into the oven and cook uncovered for 20 minutes.

6. Preparing the Potatoes: While the lamb is cooking, to a large bowl, add the fingerling potatoes, the remaining 2 ½ Tbsp lemon juice, 2 Tbsp olive oil, garlic powder and ½ tsp kosher salt. Toss until all the ingredients are fully incorporated.

7. Remove the lamb from the oven and carefully add the potatoes to the base of the baking dish.

8. Roasting the Lamb and Potatoes: Reduce the oven temperature to 350°F, cover the lamb and transfer it back into the oven. Cook for 1 hour and 10 minutes to 1 hour and 30 minutes, depending on your desired level of doneness. For medium-rare (145°F or 63°C), 1 hour and 10 minutes of cook time will result in lamb that is pink and moist. While a cook time of 1 hour and 30 minutes will yield lamb that is well-done (170°F or 77°C) or fully cooked with no pink colour remaining. For the last 10 minutes of cook time, remove the cover and cook uncovered to allow the herb, lemon and mustard crust to crisp up.

9. Roasting Time May Vary: To determine the overall cook time, select your desired level of doneness, specifically medium - rare, medium, medium - well or well done. When checking for doneness, insert your digital thermometer into the thickest part of the leg, ensuring that you avoid the bone. Remove the lamb from the oven when the internal temperature reaches just shy of 5°F – 10°F of your desired internal temperature (or level of doneness). As the lamb rests, it will continue to cook by another 5°F – 10°F and the internal temperature will increase to your desired level of doneness.

10. Creating the Mint Sauce: While the lamb is cooking, to a small bowl, add the mint, shallot, red wine vinegar, 1 ½ Tbsp olive oil, ½ Tbsp honey, ¼ tsp salt and ground pepper and whisk until fully incorporated. Set aside to allow the flavours to meld.

11. The Finishing Touch: Remove the lamb from the oven and let it rest for at least 15 minutes. Cut into desired slices and drizzle pan juices over top. Serve it alongside the mint sauce and roasted fingerling potatoes and enjoy!  

Notes:

1. Trimming the Lamb: When preparing the bone-in leg of lamb, you want to trim or cut off the fell or silver skin. This is the tough, paper-like membrane that covers the fat and the meat. When cooked, this tough membrane may result in an unpleasant mouthfeel. To remove the fell, grab a sharp paring knife and carefully slip it under the membrane to separate it from the meat. Using a paper towel for extra grip, lift and cut the paper-like membrane away from the meat and discard it.

2. Baking Dish Without a Cover: If you don’t have a baking dish or roaster with a cover on hand, simply use a 9” x 13” ceramic baking dish and cover the leg of lamb with parchment paper followed by aluminum foil. The parchment paper serves as a barrier and prevents the rub and/or crust from sticking to the aluminum foil. The crust is full of flavour and this trick will help it remain intact over the course of the roasting process.