Heat the oil in a large saucepan over medium heat. Cook the leek, celery, carrot and garlic for 10 minutes, until softened.
Add the cabbage, zucchini and VEGEMITE and stir until combined. Stir in the stock and soup mix. Bring to the boil over high heat, then reduce the heat and simmer, partially covered, for about 2 hours or until the soup mix is tender and the soup has thickened. Extra water may be required if soup becomes too thick. Season well with freshly ground black pepper.
Sprinkle with the parsley, and serve with the crusty bread on the side.
