I chanced upon the following herb at a vegetable stall at Serangoon North Ave 1 and I heard from the stall owner that this herb is good for de-toxing and the cooking method is also very simple ..
After washing and soaking off the sand, mud and dirt off the plant (roots included), put it in a pot filled with water, add black sugar and boil.
I tried it and it taste like watercress drink .. with a very strong veggie taste .. my kids do not like it and neither do I ..