Finely chop the onion, celery and carrots - you can do this in the Froothie Optimum 9400 if using. Tip the chopped vegetables into a large pan or stock pot. Put the pan onto a medium heat, add the oil and cook the vegetables until soft - around ten minutes. Chop the potato into cubes and add to the pan. Add in the tomato and shredded cabbage. Pour over the stock, season with sea salt and pepper and add the marjoram or other dried herbs. Cook for ten minutes then leave to cool slightly. Carefully pour the soup into the Optimum 9400 and blend on high for one to two minutes, until the soup is silky smooth. Add a splash of soy milk for a creamier finish.