As I labour in the spice mines of East Indian cooking, I have come across a curious one, made of a resinous gum extract from the rhizomes of a palm tree. It has a strong and bitter taste but, when cooked with other ingredients, produces a flavour a bit like onions and/or garlic and with the nose of a truffle. Some sources call it asafetida and others asafoetida. Why? And which is better?