I've had Bang Bang chicken at the Ivy and think I did an alright job of recreating it;
Bed of shredded carrots and finely sliced lettuce of your choice.
Boil a chicken breast and then chill it/allow it to cool. Slice once cool. Place on top of carrot bed.
The sauce is just smooth peant butter mixed with some toasted sesame oil, finely diced fresh chilli and some sweet chilli sauce. Do over a low heat as this micture can get to thick very easily, add butter if you need to thin it out. Pour as much on as you fancy.