Strain the cooked oxtail. Reserve the broth.
Heat the cooking oil in a pot. Saute the garlic, shallots, tomatoes and finger chili.
Pour in the oxtail broth. If there isn't enough, pour in all of the bone broth as well. For four people, you will need six to eight cups for broth for generous servings. Season with fish sauce. Bring to the boil.
Start dropping in the vegetables beginning with what takes longest to cook. I drop in the okra and taro first. The sitaw follows after five minutes. Then, after another five minutes, the kangkong stalks and eggplants. After another five minutes, the kangkong leaves and radish go in.
Add the strained oxtail to the vegetables in the pot.
Stir in the tamarind juice. Taste and add more fish sauce, if needed.
Bring to a simmer and cook, covered, for another five minutes.
Taste the sinigang broth one last time and add more fish sauce, if needed, before serving.