Getting Saucy

Balancing atop a ladder, 72-year-old Nguyen Van Bang closes his eyes to take a deep appreciative breath. Then he plunges his hand into a vat of rotting anchovies and salt. "You see, this one is only about a week old—the fish still have their eyes and tails," he says, turning over a soupy mixture between his fingers. "But they'll all decompose soon enough, don't worry." Descending, he springs to another wooden vat and turns a valve, filling a snifter with a warm amber liquid. This is prized nuoc mam , fermented for more than a year. Bang holds the liquid up to...