1. Make the lamb: Preheat oven to 400 degrees.

2. In a small bowl, mix together 1/4 cup oil with nutmeg, paprika, and fennel. Rub lamb all over with spice mixture and season with salt and pepper. Heat remaining 1/4 cup oil in a large Dutch oven or roasting pan over high heat. Add lamb and cook, turning on all sides, until seared.

3. Remove lamb from pan. Make small incisions in lamb, about 2 inches apart; alternate tucking spring onion slices or garlic cloves and rosemary into incisions. Place remaining spring onion slices or garlic cloves, onions, celery, and carrots in roasting pan and set lamb on vegetables. Add beef stock and thyme to pan and bring to a boil over medium-high heat; cover tightly with parchment paper-lined aluminum foil. Transfer to oven and cook 5 to 10 minutes; reduce heat to 300 degrees. Cook until lamb is tender and pulling away from the bone, 3 1/2 to 4 hours. Remove from oven and let stand in pan for 2 hours.

4. Remove lamb from pan and carefully remove bone, leaving as much meat in one piece as possible. Strain cooking liquid and set aside; discard solids.

5. Make the salad: Meanwhile, preheat oven to 350 degrees. Place sun-dried tomatoes in a small bowl and add enough water to cover; let stand until rehydrated, about 10 minutes. Drain, finely chop, and set aside.

6. Heat canola oil in a medium ovenproof skillet over medium high heat. Add onions and cook until charred. Add honey and cook until onions are caramelized, about 2 minutes. Add vegetable stock and vinegar to deglaze. Transfer to oven and cook until just tender, 10 to 20 minutes. Transfer to a medium bowl.

7. Meanwhile, heat olive oil in another medium skillet over medium-high heat. Add shallot and cook, stirring, until soft and translucent. Add fava beans and cook, stirring, until tender, 3 to 4 minutes. Stir in sun-dried tomatoes and remove from heat. Add to bowl with onions; add mint and season with salt and pepper. Serve with lamb and reserved strained cooking liquid.