In a large bowl, soak the beans overnight in enough cold water to cover. Drain.

Heat a large stockpot and pour in the olive oil. Add the strips of bacon and cook for a few minutes to render flavor to the soup. Remove the bacon.

Add the onions, carrots, celery, and celery root and cook over medium heat, stirring occasionally, until just tender, 3 to 4 minutes.

Stir in the garlic, tomato paste, chopped tomato and the drained beans. Tie together the basil, parsley, thyme and rosemary. Add to the pot with the vinegar and the sugar. Pour in the stock and stir to combine thoroughly. Season lightly with salt and pepper.

Cook over medium heat until the beans are tender, 2 to 2 1/2 hours, stirring occasionally, adding more stock as necessary.

Discard the herbs. Remove 2 cups of the beans and vegetables and pureé in a blender or food processor. Stir the puree back into the soup and adjust the seasoning to taste.

To serve, spoon the soup into heated bowls. Garnish with sausage, Swiss chard, or Parmesan cheese, if desired.

This recipe yields ?? servings.