The soaked rice has now expanded with the absorption of water overnight.
Prepare a damp kitchen cloth and boiling water for a steamer. Put the damp kitchen cloth on the steamer.
Strain the rice and put it on the kitchen cloth that has been placed over the steamer. Make a hole in the middle like a donut hole. Cover the rice with the extra towel on the edge.
Place the steamer above a pot of boiling water, cover with a lid, and steam for 30 minutes on medium heat.
A few minutes before the rice is done, prepare a pot of boiling water. Pour most of the hot water into the Stand Mixer bowl (setting aside the rest for later), swirl a couple of times to warm up the bowl, and let it sit until the rice is ready. Discard the hot water before placing the rice in the bowl; no need to dry the inside of the bowl.
Taste test the steamed rice. If it is cooked through (with no hard core), take it out of the steamer by holding the kitchen cloth using a pot holder; it is very hot!
Place the cooked sweet rice into the Stand Mixer bowl, then start kneading with a dough hook at the lowest setting. With a spatula and the rest of the hot water left over from heating the bowl, pat some hot water on the side of the stand mixer bowl occasionally to prevent it from sticking too much.
Keep kneading until smooth and no rice bits are left (It will take about 15-20 minutes). Always stay by the stand mixer, and tap with hot water as needed.
Prepare a Ziploc or other plastic bag. Wet your hands with hot water, grab the whole mochi from the bowl, and drop it in the bag. Using your hands or a rolling pin, roll it out to your desired thickness. Close the bag, and let it cool flat in the fridge for a couple of days, or until it becomes hard enough to cut. (Do not put it in the freezer as it will make the mochi too hard to cut)