Marinate the pork loin in 3 tablespoons char siu sauce and 1 tablespoon oyster sauce for at least 30 minutes, ideally overnight.
Heat the oven to 200°C, fan 180°C and roast the marinated pork for 20 minutes. Brush on the remaining char siu sauce, turn off the heat and leave the char siu in the oven to rest for a couple of minutes before slicing.
Heat the vegetable oil in a large saucepan over a medium heat. Stir fry the ginger for a minute until fragrant. Pour in the stock and bring it to boil.
Add in the soup seasoning mix, half of the spring onions and rice noodles. Bring the soup back to boil before serving.
Ladle the noodle soup into big bowls. Serve with the char siu slices (BBQ honey pork), coriander and remaining spring onions sprinkled on top.