For the soffritto, heat the olive oil in a large saucepan and gently fry the celery, carrot, onion, garlic, rosemary and bay leaves until golden, about 15 minutes.
Remove the rosemary sprig and bay leaves and season with salt and freshly ground black pepper.
To make the soup, add the carrots, celery, potatoes and courgettes and cook on a low heat for 10-15 minutes, stirring continuously but gently. Add the ham rind at this stage if you are including it (remember to remove it before serving the soup). Season with salt and freshly ground black pepper to taste.
Add the stock and cook over a low heat for another 20-30 minutes. Add the tomatoes and continue to cook for another 10 minutes. Serve.
