One of the world's few remaining authentic brown rice malt syrup shops is Mitoku's producer, the Uchida Toka Company, in Fukuyama, Japan. As with other traditional Japanese foods, making brown rice malt syrup is a complex craft requiring a great deal of labor, knowledge, and fine-tuned intuition.

Gunichi Uchida, head of this family-run business, begins the process of making his irresistibly sweet yet subtle, thick syrup with crushed and dried organic sprouted barley. The barley is traditionally grown and processed in the mountains around Japan's former capital of Kyoto. Organic barley grains are simply soaked in water until they sprout. They are then dried and crushed, which preserves the delicate enzymes that seeds naturally produce in order to convert their starch into usable sugars for sprouting. Uchida is particularly interested in the enzymes that change the starch into maltose, a di-saccharide sugar used by seeds for sprouting.

First, Uchida flakes brown rice and soaks it overnight. The following morning he steams the flakes for one hour, adding a little water to form a thick porridge called kayu. Then, as the porridge is gently stirred, sprouted barley is added.

The delicate enzymes in the sprouted barley are easily destroyed by heat, so Uchida does not let the temperature of his rice porridge go above 158 degrees F. After adding the sprouted barley, Uchida transfers the mixture to a vat, and keeps it at a temperature between 140-158 degrees F for several hours. During this short time, the carbohydrates, proteins, and fats of the brown rice are broken down into less complex sugars, amino acids, and fatty acids. The longer it is kept, the darker and sweeter the porridge becomes. However, if left for too long, the mixture begins to develop an alcoholic smell and taste. In fact, making rice porridge is one of the steps in the traditional process of making rice wine.

Long before any alcohol develops, Uchida's years of experience tell him it is time to stop the fermentation process by heating the mixture above 158 degrees F. (70 degrees C.). The pasteurized porridge is then transferred to cotton sacks and pressed. As the thick amber liquid drips from the press, it is collected and filtered through cotton cloth.

Finally, the clear-filtered brown rice malt syrup is cooked down for several hours, first by direct cooking and then by steaming. When Uchida feels the malt has reached the perfect thickness, it is filtered one final time and then bottled.