Heat oil in a wide 5-6 quart pot over medium flame. Saute lightly in order to soften the onions, carrots, celery root, celery, and garlic for 20 minutes, while stirring.

Add tomatoes, white beans, potato, and zucchini. Add water to cover vegetables. Add two tablespoons soy sauce and a bit of black pepper and chili powder.

Cook for half an hour.

If using pasta, add it at this point. Cook 15 minutes.