In a large bowl, combine glutinous rice flour, cornstarch, strawberry powder, and sugar.
Slowly pour in the milk while stirring until a smooth batter forms with no lumps.
Strain the batter to remove any remaining clumps.
Cover the bowl with plastic wrap and poke a few holes to prevent condensation.
Steam on high heat for 30 minutes until fully set and no wet batter remains.
While still hot, add softened butter and mix until completely incorporated.
Once warm, knead the dough by stretching and folding until smooth, elastic, and no longer sticky.
Dust a surface with cooked glutinous rice flour and divide the dough into 9 equal pieces.
Flatten each piece with your hands, then use a rolling pin to roll it out into a circle about 10cm (4 inches) in diameter, keeping the edges slightly thinner than the center.