Step 1: In a microwave-safe bowl, whisk together the glutinous rice flour and granulated sugar until well combined.
Step 2: Gradually add the water or milk to the dry ingredients, whisking continuously until a smooth, lump-free batter is formed. Stir in the vanilla extract, if using.
Step 3: Cover the bowl loosely with plastic wrap, leaving a small vent. Microwave on high for 2 minutes.
Step 4: Carefully remove the bowl (it will be hot!) and stir the partially cooked mochi mixture with a wet spatula or spoon. It will be thick and sticky in places.
Step 5: Re-cover and microwave for another 1-2 minutes, or until the mochi is translucent and very sticky, resembling a thick paste. The cooking time can vary based on your microwave’s wattage.
Step 6: While still hot, transfer the cooked mochi onto a generously cornstarch-dusted surface (a large cutting board or baking sheet works well). Dust the top of the mochi dough and your hands/rolling pin with more cornstarch to prevent sticking.
Step 7: Gently pat or roll the mochi dough into a rectangle about 1/4 inch thick. Avoid overworking the dough, as it can become tough.
Step 8: Using a sharp, cornstarch-dusted knife or a pizza cutter, cut the mochi into small squares or circles, roughly 1.5 to 2 inches in size.
Step 9: Take each piece of mochi, gently flatten it further if needed, and place your desired filling in the center. Carefully gather the edges of the mochi around the filling and pinch them closed to form a sealed ball or bite-sized piece. Ensure the seam is tight.
Step 10: Place the finished Mochi Dessert Bites seam-side down on a plate. If using ice cream, fill just before serving and enjoy immediately. For other fillings, they can be stored.
Step 11: Dust with a little more cornstarch or powdered sugar for a polished look, or serve plain. Enjoy your homemade Mochi Dessert Bites!