Crystal-Skin Dumpling Dough

The translucent, glassy wrapper of a har gow is not made from flour but from wheat starch, usually with a little tapioca starch for stretch and shine. The trick is heat: whisk the starches together, then pour in water that has just reached a rolling boil all at once and stir hard until it forms a shaggy dough - water any cooler will not cook the starch and the dough will fail. Work in a little neutral oil and knead until smooth and translucent. Keep the dough covered and warm at all times, because it turns brittle and cracks the moment it cools. Press or roll into thin rounds, fill, and pleat into the classic bonnet; a short steam turns the skin clear and glassy.