01 - Set the oven to 400°F and allow it to reach temperature before roasting.
02 - Combine minced garlic, chopped rosemary, thyme, kosher salt, black pepper, Dijon mustard, olive oil, and lemon zest in a mixing bowl to create a paste.
03 - Dry the lamb leg with paper towels and make small incisions evenly over the surface. Rub the herb paste thoroughly, pressing it into the cuts for enhanced flavor penetration.
04 - Place quartered onions, carrots, and celery evenly in a large roasting pan to create a flavorful base for the meat.
05 - Set the lamb leg atop the vegetables with the fat side facing up to allow self-basting during cooking.
06 - Pour dry white wine or chicken broth around the lamb in the pan, avoiding direct contact with the meat surface.
07 - Roast uncovered at 400°F for 20 minutes to develop a crust.
08 - Lower oven temperature to 350°F and roast for an additional 1 hour 10 minutes, or until the internal temperature reaches 135–140°F for medium-rare doneness.
09 - Transfer the lamb to a cutting board, tent loosely with aluminum foil, and allow it to rest for 15–20 minutes to redistribute juices.
10 - Skim excess fat from the roasting pan liquids, strain, and serve alongside the carved lamb for enhanced flavor.