In the meantime, heat up the oil in a wok over medium-high heat. Stir in spring onion and shiitake mushrooms. Cook until fragrant.
Add tomato then fry until a bit mushy. Pour in hot water. Cover the wok with a lid. Leave to simmer until the tomato is very soft.
Turn the heat up to high. Gently place the meatballs one after another into the soup. Boil until the meatballs are fully cooked (check one ball. Do not overcook ).
Sprinkle with salt, white pepper and coriander.
Serve it hot with well drained noodles. Add some Chinese chilli oil if you wish.
Notes
1. You may also use minced pork or turkey for this dish. 2. How to rehydrate shiitake mushrooms: soak them in cold water for at least 8 hours until very soft. Trim and discard the stem before slicing.