Canned cannellini beans transformed this otherwise long-simmering soup into an easy weeknight meal. The Parmesan rind added a deep savoriness; some grocery stores sell just the rinds, or if you have a chunk of Parmesan in your refrigerator, trim off its rind for use in the soup. If you reheat leftovers, you may need to add to additional broth, as the soup becomes thicker as it stands. Crusty bread is the perfect accompaniment.