Coat a Belgian waffle maker with cooking spray and preheat according to the manufacturer's instructions.
In a large bowl, whisk together the mochiko, sugar, baking powder, and salt.
Add the eggs, melted butter, milk, and vanilla and mix until well combined, scraping the bowl to ensure no dry lumps of mochiko remain.
Scoop the waffle batter into the prepared waffle maker, using about 1/3 cup (80 milliliters) for small waffles or 2/3 cup (160 milliliters) for one large waffle.
Close the lid to the waffle maker and cook for 4 to 5 minutes, or until the waffles are browned. Repeat with the remaining waffle batter.
Add toppings of choice- maple syrup, whipped cream, fresh fruit, or red bean paste- and serve immediately.
Leftovers can be stored, in an airtight container, in the refrigerator for up to 6 days. Reheat in the microwave or in the toaster.