Stir chicken broth, chickpeas, sweet potatoes, butternut squash, onion, ginger, garlic, nutmeg, and cayenne pepper together in a large pot. Bring to boil and cook over medium-high heat for 20 minutes. Reduce heat to medium low and cook until squash and potatoes are soft and soup flavors have blended, about 3 hours.
Blend soup using an immersion blender, or in batches in a food processor, until smooth.
