1.Cook noodles in a large saucepan of boiling water for 2 minutes, drain and refresh under cold running water.
2.Blanch prawns in a separate saucepan of boiling water for 10 seconds, then transfer to an absorbent paper-lined plate to drain. Add bok choy to water and blanch for 20 seconds, then drain and refresh under cold running water.
3.Bring chicken stock to the boil in a large saucepan, add noodles to warm through, then divide noodles between bowls. Add prawns and mushrooms to chicken stock and cook for 2 minutes, then add bok choy and stir. Arrange prawns, mushrooms and bok choy over noodles, then ladle over chicken stock and serve immediately with a few drops of sesame oil.
