1) In a slow cooker, combine stock, tomatoes, beans, carrots, celery, onion, thyme, sage, bay leaves, and half a teaspoon each of salt and black pepper. Cover and cook on LOW for six to eight hours or on HIGH for three to four hours.
2) Thirty minutes before the soup is done cooking, add ditalini, courgette and spinach. Cover and cook 30 more minutes. Remove bay leaves and season, to taste, with salt and black pepper. Ladle soup into bowls and sprinkle parmesan cheese over top. Garnish with basil, if desired.