Saute the onions celery, and carrots in the oil over medium heat for 10 minutes. Add the garlic, potatoes, cabbage, salt and pepper. Continue to saute for another 10 minutes over medium-low heat. Add the remaining ingredients. Bring to a boil and then simmer for 20 minutes (or until the potatoes are tender). At this point, you can season the soup and serve it as is. Or if you prefer a thicker soup, you can put 3 cups of the soup solids & 2 cups of the broth into a blender. Puree & then return to the soup. Bring the soup back to a simmer. Stir in the dry potato flakes to thicken the soup. Season to taste. Pour soup into bowls and garnish with chopped parsley or dill. NOTE: If you like, you can puree all of the soup to make it lighter for a first course. If the soup is going to stand on its own, leave it a little on the chunky side.