Cover dried rice noodles with cold water and let them soak for at least 4 hours, or overnight, until they are pliable and no longer chalky in the center.
Trim the ends of the Chinese chives and cut into long sections. Finely chop the tomato and the pickled mustard greens so they integrate easily into the broth.
Crisp the pork and build the aromatic base
Heat vegetable oil in a pot and fry the minced pork with chopped garlic until golden and aromatic. Stir in 1 tablespoon of light soy sauce and the salt until the pork is crisp at the edges.
Remove half of the cooked pork from the pot and set aside to use as a textured 'broken meatball' topping later.
Add the chopped tomato and pickled greens to the remaining pork in the pot. Stir-fry for 2 to 3 minutes, allowing the tomato to soften and the pickles to lightly caramelize for a deeper flavor.
Finish the broth and serve it piping hot
Pour in the water or stock and bring to a boil, skimming away any foam that rises to the surface to keep the broth clean.
Add the remaining 2 tablespoons of light soy sauce and adjust salt to taste. Slide in the soaked rice noodles and cook for 2 minutes until they are bouncy and silky.
Toss in the bean sprouts and chives. Let the soup return to a boil briefly so the vegetables soften slightly while maintaining their crunch, then turn off the heat.
Transfer to a deep bowl, top with the reserved crispy pork, and finish with a drizzle of chili oil. Serve immediately.
Notes
Noodle Selection: Look for thick rice stick noodles labeled as Jiangxi-style or Bun Bo Hue noodles to ensure they stay springy in the acidic broth.Umami Secret: Searing the pickled mustard greens with the pork and tomato creates a Maillard reaction that rounds out the sharp sourness into a deep, complex savory base.Storage Tip: If you have leftovers, store the broth and noodles in separate containers. Reheat the broth until boiling before adding the noodles for 30 seconds to refresh them without losing texture.Nutrition information is estimated based on common ingredients and serving sizes and may vary.