Cut salted vegetables into chunks and soak in water for about 20mins. Taste to see if it is too salty. If it is, soak a little longer.
Drain salted vegetables. Set aside.
In a pot of boiling water, blanch duck chunks into boiling water for 3 mins, then wash the duck again with fresh water and remove any visible blood clots.
Bring 3L of water to boil in a pot. Once boiling, add in the duck, tamarind skin and ginger and boil over medium heat for 0.5hr.
Turn heat into medium low, then add the salted vegetable, tomatoes and sour plumand boil for another 30 min or until the duck is soft but not disintegrated.
Serve when hot.
Serve when hot. Ensure all the fats of the duck are removed to avoid a very oily soup.