Soak the beans for 10-12 hours.
Boil them for about one hour and set aside. Important: do not discard the water, you will need this later.
Cut the vegetables into not to small pieces.
Put a glug of olive oil in a large casserole. Add the onion, carrot, celery, potato, leek or Swiss chard, fresh chives or wild garlic and the cavolo nero or savoy cabbage.
Add after about 5 minutes the eggplant (otherwise the eggplant will be overcooked). Let the vegetables stew on a medium heat for about 10-15 minutes.
In meantime, take 1/3 of the beans and mix them with a little bit of the boiling water into a paste. The paste will be used to thicken the soup (this is a very common use in Tuscan cuisine)
Pour a few large spoons of the beans cooking water over the vegetables; you will have a thick soup.
Add a couple of tablespoons tomato pulp for the taste and the color.
Add also the bean paste and stir everything. Add the rest of the beans and the bouquet garni, sprinkle with salt and pepper. Let the soup simmer on a low heat for another quarter of an hour.
Cut the bread into slices and then cut each slice into another half. Brush each slide with some olive oil and add to the grill for a few minutes.
Put the slices of bread into a dish and add the soup. Sprinkle with pepper of the mil.
Thanks to: De Food Madam