To make the dressing, shake the tahini and sesame oil in a jar until thoroughly combined. Add the remaining ingredients and shake vigorously until well combined. The dressing can be refrigerated until ready to use.
In a bamboo steamer, steam the capsicum and carrot for about three minutes each and the bok choy for about two minutes - take care not to overcook them.
When steamed, rinse the vegetables in cold water and drain thoroughly. Boil the noodles until soft and tender (about 4 minutes) then drain and rinse in cold water. Mix the steamed vegetables with the noodles, herbs and beansprouts.
Pour the dressing over the salad and serve.