Preheat your oven to 325°F (160°C). Pat the lamb leg dry with paper towels and season generously with salt and pepper.

In a large Dutch oven, heat olive oil over medium-high heat. Add the lamb leg and sear on all sides until browned, about 4-5 minutes per side. Remove the lamb and set aside.

In the same pot, add chopped onion, carrots, and parsnips. Sauté for about 5-7 minutes until they begin to soften. Add minced garlic and chopped rosemary, sautéing for an additional minute until fragrant.

Pour in the pomegranate juice and balsamic vinegar, scraping up any browned bits from the bottom of the pot. Stir in the Dijon mustard.

Return the lamb leg to the pot, adding the beef or lamb broth. The liquid should cover about two-thirds of the lamb. Bring to a gentle simmer.

Cover the Dutch oven with a lid and transfer it to the preheated oven. Braise for 2.5 to 3 hours, or until the lamb is tender and easily pulls apart with a fork.

Once the lamb is cooked, remove it from the pot and let it rest. Strain the cooking liquid into a saucepan and bring to a simmer. Reduce slightly until it thickens to your desired consistency.

Slice the lamb leg and serve it on a platter. Drizzle with the pomegranate-balsamic gravy, and garnish with fresh pomegranate seeds and rosemary sprigs.