Editor鈥檚 note:

Everlasting Flavors is a series profiling the condiments, sauces and spices that define Chinese cooking.

Chinese people have a lot of unique living habits, and one of them is always keeping a jar of fermented tofu in the fridge.

In Shanghai, you can go rich and bold for breakfast by snacking on fried goodies like youtiao (fried dough stick) and dabing (flatbread), or opt for a much lighter yet comforting meal of a bowl of congee, half a cube of fermented tofu and a small plate of pickled vegetables.

鈥淕rowing up I鈥檝e always been eating rice congee and fermented tofu. The simplest meal is a true comfort food dear to my heart. The congee can warm up the stomach instantly while the salty fermented tofu can stimulate the taste buds, especially in the hot summer when the appetite is not good,鈥� said Judy Wang, a Shanghai local who enjoys fermented tofu.

Congee and fermented tofu can also be a comforting late-night snack before bed.

A little goes a long way, it鈥檚 sufficient to dip the tip of the chopsticks to pick up a tiny bit of fermented tofu. Never eat a mouthful of fermented tofu because the overwhelming saltiness could destroy the beauty of the condiment as well as the palate.

Let鈥檚 take a quick look at how fermented tofu is made.

The intriguing condiment hailed as 鈥淐hinese cheese鈥� is creamy and briny with a unique wine flavor gained from the fermentation process.

The technique of tofu fermentation was created in ancient China, but the exact time is unknown. Fermented tofu became popular in the Ming Dynasty (1368鈥�1644), and the scale of production was quite large at that time.

Fresh tofu that is cut into small cubes is arranged in wooden boxes at 15 to 18 degrees Celsius to maintain a certain level of humidity so mold would start to grow on the tofu over the first two days. Five days later the pieces would be covered.

Traditional methods cannot control the quality and type of mold, hence the quality of the fermented tofu fluctuates, but modern production in a strict bacteria-free environment inoculates the good mold to avoid cross contamination of other cultures.

The next step is spreading one layer of salt in between two layers of tofu cubes, which are arranged in jars and sealed with another thick layer of salt on top for an eight-day fermentation process. The salt separates water from the tofu to harden the texture and inhibit the growth of the microbes while preventing the tofu from going bad.

Brine is the crucial element in making fermented tofu because it determines the flavor of the final product. Composed of Chinese wines such as yellow or rice wine, or sorghum liquor, alongside spices such as peppercorn, star anise and cassia, the tofu cubes are soaked in the brine to absorb the flavors.

The whole process looks quite easy, and there are people who try to make fermented tofu from scratch at home using firm textured tofu that won鈥檛 break up easily when immersed in liquid.

Besides being a delicious condiment, fermented tofu, as a soy product, contains minerals such as calcium, magnesium, iron, potassium and zinc, though the high sodium level should also be noted.

Fermented tofu, also called furu, is sold across China in every supermarket as a staple of the Chinese lifestyle. It鈥檚 the 鈥渧egetarian Chinese cheese鈥� that not only brings more vibrant flavors to dishes and meals, but also boasts some health benefits from the fermentation.

The most common types of fermented tofu are the hongfang (red fermented tofu), baifang (white fermented tofu) and qingfang (green fermented tofu).

鈥淏aifang and hongfang are what I keep in the fridge throughout the year, they are simple yet versatile condiments. I also add them into stir-fries sometimes because it brings more complex flavors to the vegetables and meat,鈥� said Zhou Li, who often cooks with fermented tofu.

Baifang originated in Guilin in the Guangxi Zhuang Autonomous Region and is regarded as one of the 鈥渢hree treasures of Guilin鈥� alongside Sanhua wine and Guilin chili paste.

Highlighting the original, simple taste of fermented tofu, plain baifang is most often eaten with rice congee, pancakes or steamed buns as a daily staple in southern China.

There are other varieties of white fermented tofu. The spicy Guilin-style fermented tofu with chili oil is very popular nationwide. It is briny, spiced and firm. While the Yangzhou-style white fermented tofu, known as zaofang, is much lighter and milder, because the addition of distilled grain brings sweetness to the salty brine.

In Yunnan, there鈥檚 the renowned Mouding furu that has a bright red-colored spicy chili coating wrapped outside the creamy and soft white fermented tofu.

The Guanghe furu from Guangdong Province is another iconic fermented tofu label in China created in 1893 by Fang Shoutang. A special culture is used to create the smooth and lingering flavor.

Originating in the Qing Dynasty (1644-1911), this glistening delicacy is only produced from November to March every year, because the air drying and fermentation require certain weather conditions. If it鈥檚 too humid and hot, the fermented tofu wouldn鈥檛 have its strong fragrance and firmness.

To neutralize the saltiness in white fermented tofu, drizzling a little bit of sesame oil and sprinkling some granulated sugar can help a lot, but not everyone can accept this sweet and savory combination.

Hongfang is another popular fermented tofu that gains its red color from the red yeast rice added in the brining liquor. The inside of the red fermented tofu, however, is actually yellow. It has softer texture and sweeter taste, which is especially appealing to children.

鈥淭he red fermented tofu is great in stews and rich braised meat dishes because the flavor is not straightforwardly salty but has a hint of sweetness. The bright color can also make the dishes look more vibrant and appetizing,鈥� said Zhou.

Classic recipes include pig trotter braised in red fermented tofu sauce, braised pork belly with red fermented tofu and water spinach stir-fry.

Qingfang is enjoyed by fewer people because of its distinct stinky smell, the origin of which is credited to Wang Zhihe in the Qing Dynasty.

It is told that Wang once stored leftover tofu in a jar in the hot summer and forgot about it. In the fall, he opened the jar to find that the smelly tofu cubes had gone greenish colored, but the taste wasn鈥檛 bad at all. Rather, it was very creamy and smooth.

Wang expanded his business selling the stinky furu. Empress Dowager Cixi favored the condiment and named it qingfang.

Qingfang is like the Chinese blue cheese. It鈥檚 eaten as a spread on pancakes and steamed buns. People seldom cook with qingfang because it鈥檚 difficult to incorporate the strong flavor in common dishes.

鈥淚t鈥檚 either love or hate, my father likes qingfang and used to keep a jar at home but my mother never touched it. He said it was smelly yet tasty, but I cannot overcome the stinky smell, too,鈥� said Zhou.

Other fermented tofu you can find

Chinese cabbage fermented tofu (baicai furu, 鐧借彍鑵愪钩): A Sichuan-style condiment that wraps tofu cubes in Chinese cabbage leaves to ferment in a clay pot with soy beans. It鈥檚 a duo of pickled cabbage and furu.

Ham fermented tofu (huotui furu, 鐏吙鑵愪钩): A specialty from Zhejiang Province that combines fermented tofu with the famous Jinhua ham, which is dark in color and has richer flavor.

Rose fermented tofu (meigui furu, 鐜懓鑵愪钩): A variation of hongfang that seasons the tofu with sugared rose petals. It鈥檚 even sweeter than the original.

Sweet wine fermented tofu (tianjiu furu, 鐢滈厭鑵愪钩): A Taiwan-style fermented tofu that鈥檚 much sweeter than common baifang. It鈥檚 fermented with sweet wine and comes with soy beans that add some texture to the soft tofu. The alcohol fragrance is also strong.