Fish Sauce (Nuoc Mam)

Fish sauce is to Vietnamese cooking what salt is to Western and soy
sauce to Chinese cooking. It is included in practically all recipes.
Prepared from fresh anchovies and salt, layered in huge wooden
barrels, the manufacture of fish sauce is a major industry. The
factories are located along the coast to assure the freshness of the
fish to be processed. Fermentation is started once a year, during the
fishing season. After about 3 months in the barrel, liquid drips from
an open spigot, to be poured back into the top of the barrel. After
about 6 months the fish sauce is produced.

The first draining is the very best fish sauce, lighter in color and
perfectly clear. [Kinda like "Extra Virgin" fish sauce. S.C.] It is
relatively expensive and is reserved for table use. The second and
third drainings yield a fish sauce of lower quality and lower cost
for general- purpose cooking. The two towns most noted for their
fish sauce are Phu Quoc and Phan Thiet. Phu Quoc produces the best
fish sauce, some of which is exported. On the label, the "nhi"
signifies the highest quality. When fish sauce manufactured in
Vietnam is not available, that of Thailand or Hong Kong is quite
acceptable. Philippine or Chinese fish sauce will not be
satisfactory. For table use and available in all Oriental groceries
is Squid Brand Fish Sauce, the best one on the market. Whatever
brand, look for the "Ca Com" on the label, which means that only
anchovies were used++an indication of the highest quality for table
use.

From "The Classic Cuisine of Vietnam", Bach Ngo and Gloria Zimmerman,
Barron's, 1979.