Heat your waffle maker according to the manufacturer’s instructions. Lightly grease with oil or butter if needed.
In a medium bowl, whisk together the sweet rice flour, tapioca starch, sugar, baking powder, and salt.
Place the egg yolks into a small bowl and the egg white into another clean bowl.
Whisk together the egg yolks, milk, melted butter/oil, and vanilla until smooth.
Pour the yolk mixture into the dry ingredients and whisk until just combined and smooth. Batter will be thick but pourable.
Using a whisk or hand mixer, beat the egg white until soft peaks form. Gently fold the whipped white into the batter. This adds air and gives the waffles a lighter texture while maintaining their chewy texture.
Spoon batter into the center of the preheated waffle iron, spread gently to the edges, and cook 3–4 minutes, or until golden brown and crisp on the outside.
Serve and enjoy. Mochi waffles are best eaten hot.