Ingredients:

  • 1 (5-6 pound / 2.2-2.7 kg) leg of lamb, bone-in
  • 2 tablespoons olive oil (30ml)
  • 4 cloves garlic, minced (approx. 12g)
  • 2 tablespoons fresh rosemary, chopped (approx. 6g)
  • 1 tablespoon Dijon mustard (approx. 14g)
  • 1 teaspoon sea salt (approx. 5g)
  • 1/2 teaspoon black pepper (approx. 2.5g)
  • 1 large onion, quartered (approx. 200g)
  • 2 carrots, roughly chopped (approx. 150g)
  • 2 celery stalks, roughly chopped (approx. 100g)
  • 1 cup chicken or vegetable broth (240ml)
  • 2 tablespoons all-purpose flour (16g) (optional, for thickening gravy)

Instructions:

  1. Score the fat cap of the lamb in a crosshatch pattern.
  2. In a bowl, combine olive oil, minced garlic, chopped rosemary, Dijon mustard, salt, and pepper.
  3. Rub the herb paste all over the lamb, ensuring it gets into the scores. Cover and refrigerate for at least 2 hours (or up to overnight).
  4. Preheat oven to 450°F (232°C). Place quartered onion, chopped carrots, and celery stalks in the roasting pan.
  5. Place the lamb on the rack in the roasting pan, fat-side up. Roast at 450°F (232°C) for 15 minutes to brown the exterior.
  6. Reduce oven temperature to 325°F (163°C). Continue roasting, basting occasionally with pan juices, until the internal temperature reaches your desired doneness (130°F (54°C) for rare, 135°F (57°C) for medium-rare, 140°F (60°C) for medium, 150°F (66°C) for medium-well, 160°F (71°C) for well-done). Use a meat thermometer inserted into the thickest part of the lamb, avoiding the bone.
  7. Remove the lamb from the oven and transfer it to a cutting board. Tent loosely with aluminum foil and let rest for at least 15-20 minutes. This allows the juices to redistribute, resulting in a more tender roast.
  8. While the lamb is resting, place the roasting pan on the stovetop over medium heat. Sprinkle flour over the vegetables and drippings, cook for 1 minute. Gradually whisk in chicken or vegetable broth, scraping up any browned bits from the bottom of the pan. Bring to a simmer and cook until the gravy has thickened. Strain gravy through a fine-mesh sieve to remove solids.
  9. Carve the lamb against the grain and serve immediately with gravy (if using) and your favourite side dishes.