Wash 1000g sweet rice for 3 to 4 times, until the water becomes clear. Soak the sweet rice in cold water overnight.
The next day, the soaked rice grains should be easily crushed with fingers. Drain the water.
Line a steamer with cheese cloth (or parchment paper), pour the soaked sweet rice over the cheese cloth. Poke some holes into the rice with your index finger, so that it can be cooked more quickly and evenly.
Steam the sweet rice for 45 minutes, or until all the rice grains turn slightly yellow and transparent.
Use a large Dutch oven pot to boil all the utensils you are going to use later for 5 minutes to kill the germs. Set aside and let cool.
Transfer steamed sweet rice to the Dutch oven pot. Set aside and let cool.
Grind a Chinese wine yeast ball into powder. Weight 4 grams of the yeast powder (about ½ of a yeast ball).
The steamed sweet rice has been cooled in the Dutch oven pot for about 10 minutes. It's still warm but not too hot to be touched. Add 750g room-temperature water (boiled water or bottled water) to the sweet rice. Mix well.
Once the steamed rice is cooled to 30 °C - 35 °C (85 °F - 95 °F. If you do not have a food thermometer, you can touch the rice with double-washed clean hands, it should feel similar to your body temperature), add the yeast powder to the rice, mix until well combined.
If your steamer has "yogurt" function or can be set at 30 °C , transfer the sweet rice to a boiled glass container, use clean hands to gently press the surface of the rice until it's even, use your index finger to dig a hole in the middle of the rice without reaching to the bottom of the container.
You can also leave the steamed sweet rice in the Dutch oven pot, similarly press the surface and dig a hole in the middle.
Sprinkle a tiny bit of yeast powder into the hole.
Tightly cover the glass container or the Dutch oven pot with 2 layers of plastic food wrap. Put the lid on if there is one.
Place them in a warm and dark place to ferment. You can set your oven at 30 °C ( (85 °F ). If your steamer has a yogurt function, which creates a 40 °C water bath, the air temperature above the water bath is about 30 °C, and that's ideal for the fermentation process.
It's okay to just leave the sweet rice under room temperature. The fermentation process is going to take longer (3-7 days) during winter time, faster during summer time (1-2 days). But make sure the temperature is no lower than 20°C and no higher than 40°C.
The plastic wrap should be bloating if you have tightly sealed the container. Check the fermentation process daily. Once the hole in the middle is at least 80% filled with liquid, the sweet fermented rice is done.
Remove the plastic wrap, you should be able to smell the sweet wine aroma immediately.
Transfer the sweet fermented rice with its wine to a clean airtight container or a pickling jar. Store in the fridge. Always use a clean spoon to get the sweet fermented rice. It can last in the fridge for 2 months. (If you seal the jar and never open it, the sweet fermented rice can last in the fridge for 1 year.)