Sauté onion, carrot, celery, garlic and potatoes in olive oil. Add tomato paste and herbs and cook until softened.
Add the vegetables – stir in chopped savoy cabbage, cavolo nero and simmer.
Meantime, in a blender add: beans and water: blend until smooth.
To the casserole add half of the cannellini beans, and the blended beans too.
Pour the stock and simmer until everything is tender and hot then season to taste with salt and pepper *
Serve on a bowl with stale or crunchy sourdough bread and pour the soup all over.
Video
Notes
*The tradition wants this to be left in the fridge overnight and then re heated, for maximum flavour, but, trust me, it taste delicious as it is. If you have any leftover it will taste even better the day after.