1. In a 4-1/2-quart pot over medium-high heat, combine oil, onion, garlic and sweet potatoes. Cover and cook, stirring occasionally, 10 min. Add salt, lime juice, honey, cumin, chipotle pepper and 3 cups broth and bring to a simmer; cover and cook until very soft, 18 to 20 min.
2. Remove from heat. Add 1 cup broth and milk. Use an immersion blender to puree the soup. (Alternately, in batches, puree soup in blender, holding lid on with a towel while blending.) Serve with cheese. Makes 10 cups.