Mix warm water, sugar, and yeast; let sit until foamy
Combine flour, baking powder, and salt in a bowl
Add the yeast mixture and a little oil to the dry ingredients
Knead until smooth and elastic
Cover and let the dough rise until doubled in size
Punch down the dough and divide into equal pieces
Roll each piece into an oval
Brush lightly with oil and fold each oval in half
Place each folded bun on parchment squares
Cover and let rise again until puffy
Steam over boiling water for about 8 to 10 minutes
Remove from the steamer and serve warm