1. Cook the pasta according to packet directions until al dente, then rinse under cold running water and drain well. Divide amongst 4 individual bowls.
  2. In a large pot, heat up vegetable oil. Saute ginger and white parts of spring onions until soft.
  3. Pour in stock and water, and bring to boil. Add chicken and mushrooms, then turn down the heat and let it simmer for 10 minutes.
  4. Remove chicken from the pot, coarsely shred with a fork on a chopping board and return to the pot again.
  5. Bring broth to the boil and add bok choy. Cook for 1 minute or until bok choy is just tender. Remove from heat.
  6. Season with light soy sauce and white pepper to taste.
  7. Divide soup ingredients evenly amongst each bowl of pasta and ladle the hot broth over them.
  8. Lightly drizzle with sesame oil. Garnish with red chillies and green parts of spring onions.
  9. Serve with lemon wedges for squeezing.