India, Aug. 12 -- What if I told you that, as a well-travelled person, you have eaten a lot of fermented fish? That the fish has usually first been left out in the sun to decompose and the final version (which is served to you) is pure extract of fish. You would look at me in disbelief. Some of you would say things like, "But I don't even eat fish, especially stinky fish!"

But no, there's no getting around it. Fermented fish has probably made its way to your gullet at some stage in your life, even if you are a vegetarian.

From the most ancient of times cooks have always realised that fermented fish adds depth and savouriness to food. Long before the birth of Christ, a condiment called garum made from fermented fish was a mainstay of Rom...