Put glutinous rice flour and cocoa powder in a bowl and mix.
Add sugar and salt, then mix again.
Gradually add warm water while kneading the dough.
Shape the dough into small round rice cakes.
Place a piece of dark chocolate in the center and wrap it.
Place the rice cakes in a steamer and steam for about 15 minutes.
After cooling, sprinkle cocoa powder on top to finish.