Put 6 cups water, the beans, barley, garlic, carrots, celery, onions, bay leaf, 11/2 tablespoons salt, herb blend, some pepper and porcini mushrooms (if using) in a slow cooker. Squeeze the tomatoes through your hands over the pot to break them down, and add with their juices. Cover and cook on high until the beans are quite tender and the soup is thick, about 8 hours.
Add the spinach and cheese, and stir until the spinach wilts, about 5 minutes. Remove the bay leaf and season with salt and pepper.
Ladle the soup into warmed bowls and drizzle each serving with vinegar and olive oil.
From Food Network Kitchens; after further testing and to ensure the best results this recipe has been altered from what was in the actual episode.