Tương Bần (Ban soya sauce) is a delicacy found in Ban Yen Nhan Ward in My Hao Town, Hung Yen province 

The main ingredient of the sauce is soybean

The other ingredients are sticky rice and salt, while it is fermented in an enzyme known as koji punch 

Sticky rice, after being soaked in water and boiled, is spread out on bamboo tray, covered with the leaves of longan or sweet potato

The boiled rice is left for three days till it turns yellow with the fungus 

The leaves are then removed to let the fungus grow freely for one more day

Soybeans are soaked in water and dried before being baked well 

The soybeans are then baked with sand at a low temperature till they turn yellow with a sweet smell, and then being soaked again for a week

Fungus and salt is added, and the mixture is put in ceramic containers, covered tightly and dried in the sun for between two and six months

Experienced soya sauce makers sometimes leave it for up to two years 

During the drying period, makers should stir the mixture every two days, but just for a minute

Sunlight is an important factor in the process. The more sunlight it gets, the better quality the soya sauce will be. From March to August is the main season for making soya sauce

The final sauce should be a dark brown colour, with a slightly unpleasant odour but sweet taste. The sauce can last for up to three years in good conditions