I made the dough for these dumplings incorporating tofu, and filled them with koshi-an (smooth sweet bean paste). If you prepare the koshi-an balls beforehand, you can make the dumplings quickly for a little snack.
Use the sweet bean paste to make 2cm balls, and freeze.
Add tofu to the mochiko, and knead until it forms a dough
(The tofu's moisture will help create the dough. Add more if necessary.)
Divide the dough into 10 portions and shape into balls. Flatten, and wrap the frozen koshi-an balls with the dough.
Put the dumplings in boiling water. When they float to the surface, remove from the pan and soak in ice water.
Drain well and serve!
Story Behind this Recipe
When I feed rice dumplings to my 3 year old son, I put anko in the center to avoid getting his mouth and face sticky from anko. He can eat it easier this way, and he stopped complaining,"No more bean paste!" It works perfectly.
The key is making the bean paste balls and freezing them beforehand. You can use unfrozen bean paste, but it will be difficult to wrap in the dough, because the dough might not be stretchy enough. It's easier to wrap frozen ones and they keep well in the freezer, so you're killing two birds with one stone. The bean paste is easy to defrost, so it's convenient to use for other recipes too. Also, the frozen koshi-an balls are delicious eaten straight from the freezer!