
In a pot over medium heat, combine beef ribs and water. Bring to a boil, skimming scum that floats on top.
When the broth has cleared, add onions, tomatoes, and fish sauce.
Lower heat, cover, and cook for 1 to 1 1/2 hours or until meat is fork-tender.
Add gabi and cook for about 6 to 8 minutes or until soft.
Add chili and radish. Continue to simmer for about 4 to 5 minutes.
Trim about 2 inches from the kangkong stalks and discard. Cut kangkong into 3-inch lengths, separating the sturdier stalks from the leaves.
If using packaged tamarind base, add into the pot and stir until completely dissolved. Season with salt and pepper to taste.
Add kangkong stems and cook for a minutes. Add leaves and continue to cook for about 1 minute. Serve hot.
Wash tamarind and place in a pot with 1 cup water. Bring to a boil and cook until soft and outer skins begin to burst.
With a fork, mash tamarinds.
In a fine-mesh strainer set over a bowl, pour tamarind and liquid. Continue to mash with a fork, returning some of the liquid into the strainer once or twice, to fully extract the juice.
Discard seeds and skins. Pour tamarind juice into the sinigang.