In a mixing bowl, whisk together 1 cup of mochiko, ½ cup of sugar, and ¾ cup of water until smooth.

Transfer the mochi mixture into a microwave-safe bowl, cover, and microwave on high for 1 minute. Stir and continue microwaving in 1-minute intervals for 3-4 minutes until thick and slightly translucent.

Stir in 1 teaspoon of vanilla extract into the hot mochi mixture, mixing thoroughly.

Dust a clean surface with cornstarch, pour the warm mochi dough onto it, and allow it to cool for 5-10 minutes.

Once cooled, divide into 6 equal pieces, flatten into disks, place a spoonful of crushed Oreo in the center, fold and pinch to seal.

Dust each formed mochi with cornstarch, place on a plate, and refrigerate for at least 30 minutes.