Heat the oil in a tall pan. Stir fry the meat in batches for approx. 2 mins. per batch, remove from the heat, season with salt. Place the mushrooms, shallot, garlic and ginger in the pan along with the meat, fry for approx. 2 mins., reduce the heat.
Add the chilli to the meat along with all the other ingredients up to and including the sugar, cook briefly. Add the water and rice vinegar, bring to the boil. Add the pak choi and soba noodles, cook the noodles until al dente.
Cook the eggs in boiling water for approx. 7 mins., rinse briefly in cold water, peel and cut in half.
Serve the soup in bowls. Garnish with the nori, spring onion, ginger and eggs.