In a medium microwave-safe bowl, combine the glutinous rice flour and sugar, ensuring they are well mixed. Gradually whisk in water until smooth.

Cover the bowl with a wet paper towel or microwave-safe plate. Microwave on high for 1 minute, stir, then repeat two more times.

Let the mochi cool for about 5-10 minutes on a surface dusted with cornstarch.

Cut the mochi into eight equal pieces and freeze them for about 20 minutes for easier handling.

Flatten a piece of cooled mochi in your palms, place a chunk of ripe banana in the center, and seal the edges.

Dust the shaped mochi with cornstarch and place them seam-side down on the surface. Chill in the refrigerator for at least one hour.