La soya sauce is associated with the formation and development of Vinh Nghiem Pagoda with a history of more than 700 years. People in the region have filtered the methods, ways of making a good kind of soya sauce from the pagoda and in the folk community to inherit, and develop into a soya sauce product that has a good reputation near and far. 

Soya sauce is the folk food of the Vietnamese people, sauce can not be lacking when eating plain rice flan, rice cake, boiled vegetable, eggplant in salt, or boiled meat ... The soya sauce is also used to make some other dishes. In the old days, all the households, and the people in the countryside knew how to make soy sauce to serve their daily meal. However, the gourmet only choose the famous soya sauce varieties of some regions in the country such as Ban (Yen Nhan - Hung Yen), Cu Da (Thanh Oai - Ha Tay), Nam Dan (Nghe An) ) ... Many people think that La soya sauce is delicious and comparable to other kinds of soya sauce mentioned above because of the cool and fresh water source that the nature had given favor for this place but the people here do say that the good quality of the sauce much dependently on the raw materials and processing techniques of the manufacturers.

Ingredients for La soya sauce that can not be replaced as the glutinous rice called nep cai hoa vang and small seeds soybean called cuc hoa vang (2-3 times more expensive than normal soybeans). Sticky rice is selected carefully, so that there are no broken seeds mixing inside. Soaking, cleaning then cooked into a sticky rice, then take out to evenly stretch on a broad flat drying basket, to naturally ferment. Then waiting until the mold rose and had the color of areca spadix. Choosing the good quality soybean, then remove the defected seeds, drying them until well cooked and let it cool before grinding ( but not ground into too small pieces), putting the mixture in to a jar and  soaking in water for a appropriate period of time for softness (until the soybean water fragrant pervades the air). Next is the processing stage (mix the mold rice with soaked sauce, adding salt to the medium level), beating well, sun drying, then putting in cool place to preserve. It takes at least a month for complete and well - done soya sauce with the best taste. The finished product can last for about 2 years without using any preservatives.