1. Warm oil in a pot over medium heat and cook sausage until browned, about 10 minutes; transfer to a plate. Add onion and celery to pot and sauté until beginning to brown, 10 to 12 minutes. Add garlic and red pepper; sauté for 1 minute.
2. Pour in broth, raise heat to high and bring just to a boil, scraping up brown bits from pot. Return sausage to pot; stir in tomatoes and beans. Bring back to a boil, reduce heat to low; simmer for 15 minutes.
3. Season soup with salt and pepper. Stir in chard; cook until wilted, about 1 minute. Stir in parsley and top with Parmesan, if desired.
Make it ahead
TO FREEZE: Do not add chard or parsley. Let soup cool. Transfer to a freezer-safe container (leave 1/2-inch space at the top) and freeze.
TO SERVE: Thaw in fridge overnight. Reheat over medium-low heat, stirring, for 35 minutes. Stir in chard and parsley; cook for 1 minute.