Pour the broth into a pot and heat.
Dice (you may also julienne, if you wish) the onion, tomatoes, carrot, celery and bell pepper.
Finely slice the cabbage.
Add all the vegetables to the broth and bring to the boil. Season with salt and / or fish sauce and pepper. Lower the heat, cover and simmer for 20 minutes.
When the vegetables are soft, taste the broth and add more salt and / or fish sauce and pepper, as needed.
Stir in a generous splash of Worcestershire sauce.