In a microwave-safe bowl, whisk together the sweet rice flour, granulated sugar, and water until completely smooth with no lumps.

Cover the bowl tightly with plastic wrap and microwave on high for 2 minutes. Remove, stir with a wet spatula, then microwave for another 1 minute until the dough becomes translucent and pulls away from the sides.

Dust a clean work surface generously with cornstarch. Transfer the hot mochi dough onto the surface and dust the top heavily with more cornstarch to prevent sticking.

Once cool enough to handle (about 5 minutes), knead the dough gently 3-4 times to smooth it out, then divide into 6 equal portions. Flatten each portion into a 4-inch circle.

In a chilled bowl, beat the heavy cream, powdered sugar, and vanilla extract until stiff peaks form, about 3-4 minutes. Be careful not to over-whip.

Place a flattened mochi circle in your palm, add 2 tablespoons of whipped cream in the center, then press a strawberry half into the cream.

Gather the edges of the mochi up and around the filling, pinching and twisting at the top to seal completely. Place seam-side down and repeat with remaining portions.

Refrigerate the mochi for at least 30 minutes before serving to allow them to set properly and develop the best texture.