Wash the beans and keep aside. Add all the ingredients, including the beans to a crockpot / slow cooker, except for the spinach and Parmesan. Put the slow cooker on high and let it cook for 4-5 hours or until the beans are cooked well. Add more water if the soup is too thick. If you are adding more water, make sure you let it cook well with the soup for about 10-15 mins. Stir in the spinach and the cheese and cook more till the spinach is wilted. This will take about 45 mins or so. Serve with some more Parmesan sprinkled on top.