1. In an electric food processor or blender, combine 2 cans worth of beans (30 ounces total), broth, salsa, and cumin. Blend until fairly smooth.
2. Poor the bean mixture, and remaining whole beans, in a saucepan and heat over medium heat.
3. Ladle soup into 4 individual bowls, and top each bowl with 1 tablespoon of the sour cream and 1/2 tablespoon green onion.