Fennel and celery balance the richness of sweet potatoes in this dish, which is best served immediately as the sweet potato pieces may lose their shape if reheated.
1. Combine sweet potatoes, fennel, carrots, celery, onion, and garlic in 3.5-qt. tagine or Dutch oven. Stir in oil and ras el hanout, and season with salt, if desired. Pour in broth.
2. Place in cold oven, adjust heat to 300°F, and cook 2 1/2 hours, or until vegetables are cooked through, stirring every 45 minutes. Season with salt and pepper, if desired.
3. Transfer to wide and shallow serving dish if using Dutch oven. Sprinkle with pomegranate seeds and mint.