Place a large ovenproof casserole pan on a medium heat with 2 tablespoons of olive oil. Strip in the rosemary leaves and fry until crispy, then remove most of it to a plate.
Peel, finely slice and add the onion and garlic. Peel the carrots, finely slice or speed-peel into thin rounds, then add to the pan and fry for 5 minutes, or until soft and starting to caramelise. Season to perfection with sea salt and black pepper.
Add the beans (juice and all), scrunch in the tomatoes through clean hands and tip in 2 tins’ worth of water. Bring to the boil, then reduce to a simmer.
Using clean hands, tear the fluffy centre out of the bread. Tear the crusty part into the soup, followed by the fluffy part a minute or two later, and mix well. Tear in half the mozzarella, give it a stir, then sprinkle over the reserved rosemary and drizzle with 2 tablespoons of extra virgin olive oil.
Pop the soup in the oven and bake for 20 minutes, or until thick and delicious, placing it under the grill for the last 2 minutes if you like a crispy top.
Tear over the remaining mozzarella, season with black pepper, and serve up in nice bowls.