01 - In a large stockpot, bring 6 cups of water to a rolling boil. Add the pork chunks, skimming off any scum or impurities that rise to the surface for a clearer broth.
02 - Add quartered tomatoes and onions to the pot. Reduce heat to maintain a gentle simmer and cook for 20 minutes, or until the pork begins to feel tender when pierced with a fork.
03 - Stir in the sliced daikon radish and continue simmering for 10 minutes. The radish should become slightly translucent but still retain some crunch.
04 - Add the eggplant slices, trimmed string beans, and green chili peppers (if using). Simmer for 5 minutes, allowing the vegetables to cook through while maintaining their texture.
05 - Mix in the tamarind soup base until fully dissolved. If using fresh tamarind pulp, mash it in a small amount of water, strain the liquid into the soup, and discard the seeds and fibers.
06 - Season the soup with fish sauce, salt, and freshly ground black pepper. Taste the broth and adjust the seasoning as needed, balancing the sour, salty, and savory notes.
07 - Add the spinach or kangkong leaves and simmer for 2-3 minutes until just wilted. Avoid overcooking to preserve the vibrant color and fresh texture of the greens.
08 - Ladle the hot sinigang into serving bowls. Serve immediately with steamed white rice on the side for a complete comforting meal.