In a large pot, sauté the onion, celery and carrot in abundant olive oil over gentle heat until soft, along with the pancetta and leeks if using. Salt the aromatics lightly as you sauté them. And make sure they don't brown.

Now add the shredded Tuscan kale and stir. Let it simmer with the aromatics for a minute or two. Then add the Savoy cabbage and do the same.

Add enough water (or broth) to just cover all the vegetables, allong with the potatoes. Stir in the tomato paste (or puréed tomatoes). Raise the heat to medium and simmer the vegetables until tender, about 45-60 minutes.

Take half your cannellini beans and purée them with some of the their cooking liquid. (If using canned beans, use water.) Add the purée to the soup along with the rest of the beans. Simmer for another 15 minutes or so.

By the end of its simmer, the soup shoudl be quite thick but stilll have ample liquid. Top it up with water or broth from time to time if and when needed.

When the soup is done, you can start to assemble the final dish. Place bread slices at the bottom of a a good sized casserole, preferably of terracotta.

Then ladle over the soup to cover.

Let the soup rest for several hours or overnight.

Now here's the part that gives ribollita its name:

When you are read to eat, gently re-heat the soup. As the soup heats up, add a glassful of water and mix it up with a wooden spoon, which will break up the bread and mix it in with the rest of the ingredients. Taste and adjust for seasoning.

The result should be quite thick, almost more a stew than a proper soup. Nevertheless, you may need to add additional water or broth as you mix to loosen the soup a bit and prevent scorching.

Serve your ribollita while still nice and warm, drizzled on top with a drizzle of oilve oil and, if you like, some freshly ground black pepper.