Ribollita

Discard any damaged leaves from the cavolo nero, and cut out and discard the stalks. Chop the cavolo nero leaves roughly.
Dice the whole head of celery, destringing any rough outer celery stalks and reserving the leaves for garnish.
Peel and dice the onions and carrots
Peel the garlic and slice thinly.
Put about 5 tablespoons of olive oil in a large pan, and sweat the vegetables over a low heat, stirring from time to time for about 20-25 minutes. Do not allow them to brown.
Drain and chop the tinned tomatoes, then add the tomatoes and the can juice into the pan, continue to cook for about 30 minutes.
Add half of the cooked cannellini beans and enough of their cooking liquid to cover, season with salt and pepper, and simmer for another 20 minutes.
Blitz the remaining amount of cannellini beans in a food processor to a coarse puree, and stir into the soup.
Add a slightly stale ciabatta load into bite-size pieces, and enough boiling water to achieve a very thick soup consistency.
Add olive oil, 2-3 tablespoons at a time, stirring in and tasting between additions, adjusting the seasoning as needed.
Serve in large bowls with chopped celery leaves scattered over.
Offer olive oil at table if liked.