Kaffir lime leaves : the mystery resolved.
For months I thought about the distinct taste in the mango panacotta I had at Blakes. It was definitely Asian, but I could not place it. Not mint, basil, or balsam. It was an unusual flavour to have in desert, and I remember it in the little Thai pancakes I'd eaten as a child. I'd used them whole in curries before, but the piquancy of the leaves is revealed only when they are shredded. I'm not sure why I got as excited as I did (enough to write about it), but it was such a bloody relief to have suddenly made the association while chopping fresh herbs for grilled squid.