The first time I had lunch in the eastern Chinese city of Shaoxing, I couldn't believe what I was eating. I'd gone there with some friends to investigate shaoxing wine, the mellow brew of fermented glutinous rice whose historical roots date back some 2,500 years. After a tour of a wine factory, we dropped in for lunch at the Xianheng Tavern, a restaurant specializing in traditional Shaoxing cooking that is run by chef and food-culture maven Mao Tianyao. Given the rich diversity of China's food traditions, I was expecting Shaoxing to have its fair share of local delicacies. But nothing had prepared me for the sensory assault of the city's chou mei—"stinky and fermented"—flavors.

I'll skirt over the relatively run-of-the-mill "stinking tofu" (chou dou fu) and plunge right into those dishes that really amazed me. First, there was the fermented tofu skin, mei qian zhang, which can be translated as "fermented thousand layers" or, as the Xianheng menu describes it, "mildew and rotten" tofu skin. It looked innocent enough, arrayed in yellowish layers on a bed of minced pork and served right from the steamer, but it had a fetid, ammonia smell and a sharp, stinging taste that was both scary and bewitching. It was a little reminiscent of the rind of a very ripe Stilton, but at the same time utterly alien to Western palates. As I tasted it for the first time, my brain floundered amid contradictory impulses of disgust and desire.

Even more extraordinary were the fermented or "mildew and rotten" amaranth stalks (mei xian cai geng). These gray-green tubes of overgrown vegetation had a weird, stealthy smell unlike anything I'd previously encountered. Overcoming my revulsion, I put one in my mouth and, following my host's instructions, sucked the fibrous tubes to extract the few shreds of decomposing green skin that clung to them and the soft, disintegrating pulp that filled them. The flavor was almost indescribable, rotten and pure, disturbing and momentously delicious at the same time. I was hooked at first bite.

Within culinary circles, Shaoxing is celebrated as the old gastronomic heartland of Zhejiang, the southern province near Shanghai that forms part of the sophisticated Lower Yangtze region. Shaoxing is also famed as the center of the ancient Yue kingdom, the birthplace of the great modernist writer Lu Xun, and one of the cradles of Chinese civilization. Despite its illustrious history, the city is known less for its haute cuisine than for the humble fermented foods that are rooted in a history of hardship and thrifty living. Among them are dried, salt-fermented greens (mei gan cai), which have an umami taste that can be as strong as soy sauce. They are simmered in soups, steamed with pork, and used as a seasoning in stir-fries and braises. Small amounts of dried and salted fish, salt pork, and cured ham are all cooked with blander ingredients to lend them a delicious intensity of flavor. There is also the famous "yellow wine" (huang jiu), which is traditionally served in pewter jugs and is a perfect accompaniment to the strong-tasting local foods. Both the wine and the fermented rice grains left over from its making are used as kitchen seasonings.

The precise origins of many of these fermented specialties are obscure, but colorful legends fill the gaps in the written record. A local story dates the discovery of edible rotten amaranth stalks, for example, to the Spring and Autumn Period in the first millennium _B.C., when the king of Yue was captured after a military defeat and taken as prisoner to the neighboring kingdom of Wu. The Yue state had been impoverished by war, and people had to grub around for wild vegetables to survive. During this time, so they say, an old man gathered some wild amaranth stalks, ate their tender leaves, and couldn't bear to throw away the tough, inedible stalks, so he stashed them in a clay pot. Some days later, he noticed a beguiling aroma coming out of the jar. Hungry as he was, he took the stalks, steamed them, and found them to be uncommonly delicious.

One shocking origin myth concerns the Yue king Gou Jian, who spent three years in captivity after the war. The story is long, complex, and frankly too gross to tell in detail. Suffice it to say, it involves the Wu king's excrement and what Gou Jian did with it to solve the riddle of his illness and earn his freedom. When news of what had happened reached Yue, Gou Jian's countrymen felt sick with humiliation, and they decided to eat their rice with stinking foods from then on as a sign of their shame.

The heady, rotten flavors of my first lunch in Shaoxing made a deep impression on me, and I was back in the city a few months later, hungry for more. I queued up in the street for deep-fried stinky tofu slathered in chiles. The stalls aren't hard to find—you can smell them from two blocks away. By now addicted to rotten thousand layers, I ate them at almost every meal. And I visited a producer of fermented amaranth stalks, Shen Huanjiang, to find out how they were made.

Shen told me that amaranth plants are allowed to grow tall at the end of the season, and their waist-high stalks are gathered just before they go to seed, chopped into bite-sized chunks, and soaked in cold water until they become frothy. They are then rinsed, drained, and sealed in a clay jar to ferment. The timing here is critical—too short, and the stalks remain hard; too long, and their skin and pulp simply dissolve away. Afterward saltwater is added, and they are left in the jar for another couple of days before being steamed and eaten. Shen brought out a basinful of the stalks in their lu, or fermenting brine, to show me. The stalks themselves had a faintly unpleasant odor, while the lu, green as a pea soup but pungent as a blocked latrine, smelled so disgusting that it made me want to vomit.

As it happens, though, the lu is the most important product of the fermentation, a master liquid that can be used to ferment and make stinky all kinds of other ingredients, including tofu, bamboo shoots, and gourds. Over my several visits to Shaoxing, Xianheng chef Mao fed me many of them, and they were all wildly exciting in that same disconcerting way. We ate steamed stinky gourd, stinky yu choy stalks stir-fried with amaranth leaves, stinky vegetable husks. I struggled to think of taste equivalents to these foods in other culinary traditions, although their heady, nice-nasty intensity reminded me of the thrill of durian, hung game, and smelly farmhouse cheeses.

Sadly, it seems that the appetite of Shaoxing locals for these smelly foods is fading. Only a generation ago, almost everyone in Shaoxing ate rotten amaranth stalks, and most people made rotten thousand layers at home. But with rising living standards and the ready availability of meat in the post-reform era, they are falling out of fashion. “It's mainly old people and peasants who eat them these days,” said a young man I chatted with in a local Starbucks. “By the next generation they'll be completely forgotten.”

They still inspire passion, however, in their devotees. Chef Mao, also the author of several books about Shaoxing's culinary culture, is rapturous in his descriptions of foods like stinking tofu, which he calls “an exotic among everyday things” with a “lovable stench.” His restaurant is committed to preserving the region's culinary heritage and offering a taste of old Shaoxing. And despite my initial trepidation, I think Shaoxing's stinky flavors are among the most thrilling I've come across in 20 years of eating in China. But how ironic if these delicious foods, once a critical part of the local diet, end up surviving only as occasional treats for curious thrill seekers and foreign visitors like me.