Wash the potatoes and remove their sprouts.
Wrap each potato individually in plastic wrap and place all of them on a microwave-safe plate. Microwave the potatoes until they are cooked through (about 3-6 minutes on 1000 watts, depending on the amount and size of the potatoes).
Remove the plastic wrap from the potatoes and let them cool until they are easy to handle. While the potatoes are still warm, peel off the skin, and put them in a bowl. Mash them with a fork, potato masher, or pestle until they become smooth.
Mix the starch with water until dissolved. Add the dissolved starch and salt to the bowl (salt is not necessary if you plan to serve the dish with a sweet soy glaze), mix well, and shape into 0.8 inch (2cm) thick rounds, about 1.4 oz. (40g) each.
(When enjoying with a sweet soy glaze) Mix the starch with water until dissolved. In a pot, combine sugar, soy sauce, and water, and bring it to a gentle boil over low heat. Gradually add the mixture of starch and water to the pot while stirring to thicken the glaze.
Heat oil in a pan. Once the pan is hot, add the shaped potatoes and cook over medium heat until browned on both sides.
(When enjoying with a sweet soy glaze) Serve on each plate and drizzle with the glaze.