Nam Pla น้ำปลา
If there's any one key ingredient that is critical to cooking Thai food, it is fish sauce. This is a must-buy ingredient. It smells terrible, but makes make Thai food taste great.
Fish sauce is made from small fish and salt fermented for a long time. My mother makes hers in a big earthen barrels, the size that would fit a person. She would let it sit in the sun with salt. She would add pineapple to help digest the fish. After a year, she would extract the juice, filter and boil. That would be her gift for every occasion. Good fish sauce should be clear and brownish in color. A really good fish sauce should have a good fishy smell!
Fish sauce is not new, it was very popular in around the Medeterranian in Roman times. I once heard a report that the fishermen of Galilee were catching fish to be made into fish sauce.
In Thailand, the gourmands and well to do folks buys boutique fish sauce. Unfortunately, the boutique fish sauce places are too small to make it outside of Thailand. If I could I would love to import my mother's fish sauce.
Tipparos was the first brand that made it to the market and eventually to most people's kitchen - when people stopped making it themselves. There are now a number of other great brands available available. Since Tipparos was the first, you sometimes see a other brand which try to copy their original bottle's shape and mimic them with names like "Taperos" or "Tips".