In a large skillet set over medium-high heat, cook the pork in a drizzle of oil, breaking it up with a spoon until it's no longer pink. Add the garlic, ginger and half the onions and cook until the pork is turning dark and crispy.
Add the soy sauce, vinegar, chicken stock, peanut butter and peppercorns or chili flakes and cook, stirring, until the peanut butter melts and the sauce is smooth. Taste and add more soy sauce if it needs salt, or vinegar (or a squeeze of lime) if it needs more acid. Add a splash of water if it seems too thick.
Cook or soak the noodles according to the package directions. Drain well and serve topped with the pork mixture, the remaining green onions, and a small handful of peanuts and cilantro.