• 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 about 1 1/2 to 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 2 to 3 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 and continue to cook for about 1 minute. Serve hot.

If Using Fresh Tamarind

• 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.