Put plenty of cornstarch on a large cutting board.
Put the shiratama flour in a heatproof container, and add water slowly. When the flour and water have been thoroughly combined, add the sugar and stir it in.
Cover loosely with plastic wrap and microwave (at 600W) for 2 minutes. Take it out and mix with a wooden spatula. Microwave for another minute and mix again.
When the dough becomes shiny like this, it's good.
Moisten a wooden spatula, and drop the dough on top of the cornstarch bed made in step 1. Flatten it as much as possible.
Dust the top of the dough with cornstarch, and flip over. Lift up the edges with your hands. It will stretch out a lot, so don't lift it too high, and spread out the dough. It's very hot at first, so be careful.
Repeat step 6, and neaten the dough with your fingers as you spread it to 2 to 3 mm thick.
When the dough has cooled down completely, cut it out using a small soup bowl or the equivalent.
Remove the surrounding dough. If you are going to freeze the dough at this point, go to step 10. If you're going to make the dumplings right away, go to step 11.
To freeze the dough, put a piece of plastic wrap between each piece of dough, wrap tightly and freeze.
To wrap: Put a ball of ice cream in the middle of a piece of dough. To make a neatly shaped dumpling, use a portion of ice cream that's as rounded as possible.
Pull up the edges to the opposite sides and pinch together securely. Freeze the dumplings as soon as they're wrapped, and take them out when serving.
They look like this when they're cut.
I tried using a mini-yukimi daifuku case. I cut out the dough for these with a 8cm diameter cup.
A big success! They came out so evenly! If you have a Yukimi daifuku case (to mold the ice cream), the dumplings will turn out very nicely.
Story Behind this Recipe
I live overseas, and my favorite Yukimi daifuku costs 3 times what they cost in Japan, so I really wanted to make them myself, and I was able to do so.
In steps 6 and 7, the dough is very hot, but it cools down quickly. The dough is very easy to handle, so work patiently, trying not to rip it. When freezing the dough, try to wrap it up as air-tight as possible. 100 g of castor sugar may seem like a lot, but this prevents the dough from becoming hard, plus it makes working with the dough in steps 6 and 7 easy. If you are making it with the "Best Gyuuhi - Recipe ID: 336073," which reduces the sugar to 80 g, wait until the dough has softened at room temperature first before eating.