Add about 1/2 cup ube ice cream to a microwave-safe bowl. Microwave in short intervals (20–30 seconds at a time), stirring in between, until fully melted.
Add mochiko to the melted ice cream and mix until smooth and lump-free.
Cover the bowl with plastic wrap and poke a few holes for ventilation. Microwave for 1 minute. Microwave again for 20 seconds. Repeat in 20-second intervals as needed until the dough becomes thick, sticky, and slightly translucent.
Let it cool until it’s safe to handle. It should be warm but not hot.
Lightly dust a surface with starch (or use parchment). Roll out the dough to an even thickness.
Cut into 2–4 pieces. Place a scoop of ube ice cream in the center of each piece.
Gently stretch and pinch the dough around the ice cream to seal it completely.
Place wrapped mochi on a parchment-lined tray and freeze until firm.
Let it sit at room temperature for about 5 minutes before eating for the best texture.