1. Heat a large stockpot over medium heat and add the oil. When oil is hot, add onion, fennel, chard stems, carrots, celery, and garlic and cook until tender, about 10 to 15 minutes.
2. Add beans, broth, and chard leaves and bring to a gentle boil. Maintain a simmer for about 10 minutes. Turn heat to low and cook, partially covered, until vegetables are meltingly tender, about 45 minutes to 1 hour.
3. To serve, ladle soup into bowls. Sprinkle with basil, and serve Parmesan and lemon wedges on the side.
Source: fresh magazine January, February 2010