First, soak the glutinous rice overnight.Soaking makes the rice more tender after steaming.

After soaking, spread the rice evenly on a steamer tray lined with cloth and create holes in it. Steam for 30 minutes or until the rice becomes soft and sticky. Use steaming equipment, and avoid using a rice cooker for this step since it may affect the taste.

After steaming, transfer the rice to a clean pot and let it cool. Stir it with a clean spoon to separate the grains.

Then, gradually add 500 ml of water, adding it in two batches, and mix gently each time until well combined. If using your hands, be sure to wear clean plastic gloves to avoid contamination.

Grind the Shanghai yeast balls into powder. Use only 2g of yeast and mix it thoroughly with the rice. Do not add too much yeast since it can make the rice taste sour, especially in the summer.

Once mixed, flatten the rice mixture, create a small hole in the middle, and cover it twice with plastic wrap. Creating a hole up to the base of the container helps you check whether liquid has been produced during fermentation. The liquid should fill the hole you made. Moreover, covering it with plastic wrap twice prevents contamination while allowing enough oxygen to activate the fermentation process.

Let it sit on the counter for 2 days. Ideally, it should be placed in a warm environment and away from sunlight. You will notice the rice turns from dry to wet since it is producing liquid. Moreover, the rice should float to the top after producing liquid.

After 2 days, taste it and check if it is sweet. If it is not sweet, you may need to ferment it longer. Depending on the temperature of the environment, the duration of fermentation can take 2 or more days.

Store in a clean glass jar or any airtight container and refrigerate as soon as possible to stop the fermentation process. The best sweet taste is enjoyed during the first week.