Peel the sweet potato and cut into 1 cm dice. Soak in cold water for about 10 minutes to get rid of any bitterness.
Drain the sweet potato, and put into a bowl with the sugar and mix well. Leave for an hour or so until moisture is drawn out of the sweet potato (we will use the liquid).
Put water (not listed) in a steam-earthenware pot (or a steamer), and line the rack with kitchen parchment paper.
Add water, flour, and shiratamako to the bowl with the sweet potato.
When the steamer comes to a boil, put lumps of dumplings that are the size you like on the parchment paper.
Steam over medium heat for about 15 minutes. If a bamboo skewer stuck into a piece of sweet potato goes through easily, the "sticky ogre dumplings" are done.
Story Behind this Recipe
We received big sweet potatoes as a gift, so I tried making a regional speciality of my hometown Nagoya, ogre dumplings, with them.
You can also use a regular steamer. Be sure to draw the moisture out of the sweet potato in Step 2, and don't throw out that liquid. You can adjust the chewy-stickiness with the amount of shiratamako added, and the sweetness with the sugar. When I tried making these, I was so surprised that it's so easy.