Make pork: In a large skillet or heavy base non stick pan over medium-high heat, heat vegetable oil. Add pork, breaking up the meat with a wooden spoon. Cook until meat is deeply golden and crispy, then add hoisin sauce, vinegar, and soy sauce. Cook until all liquid has evaporated.
Make sauce: In a large bowl, whisk to combine all ingredients.
Cook noodles according to package instructions and add to bowl with the sauce, tossing to coat noodles in the sauce.
Divide noodles between serving dishes and top each with pork. Garnish with coriander and chopped nuts, and spring onions, and drizzle with more chili oil, if desired.
