1 cup Japanese short-grain sweet (glutinous) white rice (mochi gome), coarsely ground in a clean spice or coffee grinder and soaked in plenty of water for 30 minutes
1/4 cup potato starch (katakuriko)
2 tablespoons soy sauce, sugar, or roasted soybean powder (kinako)
8-to 10-quart steamer pot
24-inch square of muslin
Large sturdy wooden bowl and a large pestle or meat pounder for pounding the mochi
Remove the basket from the steamer pot, add 2 inches of water to the pot, and bring to a boil over high heat. Soak the muslin under running water, wring it out, then drape it inside the basket, creating a lining. Drain the ground rice, scoop it into the lined basket, and spread it out evenly. Place the basket in the pot, reduce the heat to medium, cover, and steam for 40 minutes. Remove the pot from the heat and let the rice rest in the steamer for 5 minutes. Using the muslin liner, lift the rice out of the basket and turn it into the bowl. The bowl must be roomy enough for you to pound the rice freely without spilling. Using the pestle or meat pounder, begin to pound the rice steadily. Continue pounding until the rice is smooth (or mostly smooth), bouncy, and very sticky, about 10 minutes. If the mochi is too dry and firm to pound effectively, add some warm water and continue pounding. Sprinkle the potato starch over a work surface. Wet your hands and move the mochi onto the starched surface. Now dry your hands and lightly knead the mochi into the starch until it is no longer exceedingly sticky to the touch. Divide into 8 equal pieces, roll into balls, and serve with a little soy sauce, sugar, or soybean powder.