Slow-Roasted Lamb with Rosemary and Parkland Mint Sauce

By AislePrompt Editorial · Published 2026-05-07 · Updated 2026-05-07

How this recipe was made — this recipe was drafted by AislePrompt's AI-assisted pipeline from technique templates and USDA-sourced nutrition data, and published by AislePrompt Editorial — see how AislePrompt recipes are drafted and published.

Succulent slow-roasted lamb infused with rosemary, paired with a refreshing mint sauce reminiscent of London's royal gardens. This British-inspired lamb recipe, ready in about 170 minutes, pairs leg of lamb, fresh rosemary sprigs, garlic cloves, sliced for a weeknight-friendly dinner that comes together with one pan and minimal cleanup. Each serving lands at about 480 calories and feeds 6, so it slots cleanly into a weekly meal plan and pairs well with a quick salad or grain on the side. Tap "Plan a meal with the AI" below to drop this recipe into your week and send the ingredients straight to Instacart. Nutrition values are approximate, calculated from USDA FoodData Central (fdc.nal.usda.gov) — verify against ingredient labels for any health-driven dietary plan.

Prep: 20 min Cook: 150 min Serves 6 British cuisine 480 cal/serving

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Ingredients

4 lbs leg of lamb
4 fresh rosemary sprigs
6 garlic cloves, sliced
3 tbsp olive oil
2 tsp salt
1 tsp black pepper
1/2 cup fresh mint leaves
2 tbsp white wine vinegar
1 tsp sugar
1/4 cup water

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Instructions

Step 1: Preheat oven to 325°F. Using a sharp knife, make 12 small incisions all over the 4 lb leg of lamb and insert 6 sliced garlic cloves and 4 fresh rosemary sprigs evenly.
Step 2: Rub the lamb with 3 tbsp olive oil, then season generously with 2 tsp salt and 1 tsp black pepper. Place in a roasting pan and roast for 2 to 2.5 hours until an internal temperature of 135°F for medium-rare is reached.
Step 3: While the lamb cooks, prepare the mint sauce by finely chopping 1/2 cup fresh mint leaves and combining them with 2 tbsp white wine vinegar, 1 tsp sugar, and 1/4 cup water in a small bowl. Stir until sugar dissolves and set aside.
Step 4: Remove the lamb from the oven and cover loosely with foil. Let rest for 15 minutes before slicing. Serve with the mint sauce drizzled on the side for a classic pairing that evokes the tranquility of London's royal parks.