1. Sort and wash beans; place in a large bowl. Cover with water to 2 inches above beans; cover and let stand 8 hours. Drain.
2. Combine beans, broth, and next 5 ingredients (through chile) in an electric slow cooker. Cover and cook on LOW 10 hours. Discard bay leaves. Stir in juice and salt. Ladle 1 1/2 cups soup into each of 6 bowls; sprinkle each with 2 teaspoons chopped cilantro. Top each serving with 1 1/2 teaspoons sour cream. Garnish with cilantro sprigs, if desired.