Heat the oil in a large pot over medium heat. Add the leeks and sauté until lightly browned.

Add the garlic and sauté for another minute.

Place the cauliflower, potatoes, knob celery, parsley roots, and parsnip into the pot. Cook for about twenty minutes, stirring every so often.

Add the chicken broth, six cups of water, salt, soy sauce, and white pepper. Bring to a boil. Cover loosely and simmer for one hour.

Turn off the heat, add the margarine if using, and blend very well until silky smooth.

Top with a drizzle of olive oil, if desired.