I think, and the internet seems to back me up on this, that purple sweet potato is taro. So I was expecting that lovely unusual, cereally flavour I got with the bubble tea and was slightly disappointed. A similar flavour is there, but it is very mild. On reflection, I think I expected too much and had I not had such a craving for taro bubble tea when I looked at this biscuit, I would have found it pleasingly purply in itself.