Wash watercress thoroughly as leafy veggies tend to trap a lot of dirt.
Blanch pork ribs and chicken bones.
Place all the ingredients (except the condiments, dried scallop and watercress) into a soup bag. Place the soup bag, together with dried scallop and watercress to the soup pot and bring the soup to a boil.
Simmer for 2 hours on low heat.
Add fish sauce/ salt to taste.
Notes
If you prefer the watercress to be green and crunchy, you may want to reserve half the bunch of watercress for adding into the soup about 15min before serving.
Recipe by at http://simplymommie.com/2010/01/watercress-soup.html