Q: "What is fish sauce, and can I substitute something else for it? I'm a vegetarian and I don't eat fish."Tracy White
A: Fish sauce is an essential ingredient in Southeast Asian cooking. It's known as nam pla (Thailand) and nuoc mam (Vietnam). It's made by fermenting small, whole fish in brine, and the resulting liquid is matured in the sun before bottling. While it sounds pretty awful, fish sauce actually adds amazing flavour to dishes and sauces. Once you get used to using it, you'll find it a bit of a pantry essential, especially in things like Thai curries, where it adds depth of flavour. You can find it with the soy sauce in the supermarket.
For vegetarians, instead of fish sauce, try a light soy sauce. I would use about half the quantity the recipe specifies, as soy sauce is a bit stronger in flavour.