Soak the beans in 2 quarts of water overnight, and then boil them until tender, about 45 minutes to 1 hour. Rub 3/4 of the beans through a sieve and put the puree back into the cooking water. Put aside the remaining whole beans. Brown the garlic and the chopped onion in 8 tablespoons of oil, and as soon as they have softened, add 2 tablespoons of tomato puree diluted with a glass of warm water. Add the very finely chopped carrot and the celery, the cabbages, chard, and the potatoes. Season with salt and pepper, cook for a few minutes and then add the pureed beans. Continue cooking for an hour. When the vegetables are well done, add the sliced bread and the whole beans previously put aside. Mix well, pour into a soup tureen and serve with a touch of extra-virgin olive oil and the thinly sliced onion passed around separately.
Recipe courtesy of Il Latini