Preheat oven to 150c. Place lamb into a roasting pan, drizzle with a little olive oil and rub over cumin seeds, salt and freshly ground pepper. Place into the oven and roast for 2 hours, add tomatoes and eggplant to the roasting pan, drizzle with olive oil and season with salt and pepper. Cook for a further hour or until meat is falling from the bone and vegetables are tender.
Meanwhile cook couscous in boiling salted water until tender, about 30 minutes. Drain and set aside.
For yogurt and garlic sauce, using a mortar and pestle crush garlic to a fine paste, stir through yoghurt and olive oil and season to taste with sea salt and freshly ground black pepper.
To serve stir couscous and herbs through tomatoes and eggplant, season to taste and serve with pulled lamb drizzled with yoghurt and garlic sauce.