Caldo Verde - Portuguese Kale Soup

Chop kale, removing all stems. Chop onion and garlic and cook over low heat in a soup pot until softened. Add chicken stock and kale and whole sausages. Cook for an hour or so, adding liquid if necessary. Add halved potatoes the last 15 minutes or until tender. Remove sausages (and potatoes if you prefer to keep them whole in the soup). Transfer soup in small batches to blender or food processor and puree. Be careful - soup is very hot! (Only fill blender to about a third capacity) Return to pan, reheat, and finish by whisking in sour cream. Slice sausages, and return to soup. Serve.