If using dried beans, soak over night, rinse and fill pot with clean water. Simmer on low for 6 hours, or until cooked through.
Roast the sweet potatoes in a 450° oven for 20 minutes. Allow to cool, then remove skins.
Drain beans, add the sweet potatoes, seasonings and broth.
Using a stick blender, or hand blender, blend until smooth.
Squeeze lime juice over the soup.
Serve with tortilla chips on the side.