Scoop the chocolate ice cream using ice cream scoop about 1/3 cup, then place it into a paper cup. Repeat for remaining 5 paper cups.
Freeze for about 30 minutes.
Mix glutinous rice flour with cocoa and powdered sugar in a bowl then add water.
Wrap the steamer lid with a cloth so the water from steaming doesn't enter the mochi mixture. Steam mochi mixture in a steamer for about 15 minutes.
When it is done, pour cornstarch into a tray so the mochi won't stick.
Transfer the mochi into a tray and dust it with cornstarch on top of the mochi and also dust the cornstarch on a rolling pin so the mochi won't stick to it.
Roll mochi to a thickness of about 2-4 mm with a rolling pin.
Using a pizza cutter, cut mochi into 6 15cmx15cm square.
Remove the chocolate ice cream from a paper cup.
Place ice cream in the center of a mochi dough square. Gather mochi dough together to cover the ice cream completely, pinch the edges together at the base.
Cut off any excess dough. Then wrap it with cling wrap.
Repeat with the remaining chocolate ice cream and mochi dough squares.
Freeze to firm the chocolate mochi ice cream.
Your chocolate mochi ice cream is done. Take out from the freezer to enjoy it whenever you want.