In a microwave-safe bowl, combine the ¾ cup glutinous rice flour, ¼ cup sugar, and ¾ cup water. Whisk together until combined.
Microwave the bowl on high for 1 minute. Remove, and use a spatula to mix together. Lumps are expected. Return to the microwave and heat another 30 seconds. Remove and stir. Return to the microwave for 15-30 second increments until all liquid becomes a sticky dough.
Ensure the dough is cool enough to handle before proceeding. Sprinkle your board generously with cornstarch, and roll out to about ¼" thickness. Cut out roughly 2" circles.
Add roughly ½ tsp filling to the center of your mochi dough circle. Fold it up and press together the seams. Set aside and repeat for all remaining filling and dough.
Serve the mochi fresh. Because of the moisture in the strawberries they will not keep. If desire to make them ahead or keep for more than 8 hours, store them in the freezer and thaw before serving.