"For tender results, use a moderate-protein all-purpose flour, such as Gold Medal® or King Arthur®, when making these buns. This recipe uses both yeast and baking powder to ensure they rise in the steamer. Serve slightly warm or at room temperature, filled with your favorite fillings."
Stir together yeast and water in a small bowl; let stand 5 to 10 minutes. Whisk in 2 tablespoons of the oil.
Pulse flour, sugar, baking powder, and salt in a food processor a few times to combine. With machine running, pour yeast mixture through feed tube. Start slowly, then pour faster. Process until a dough ball forms, sides of bowl are nearly clean, and dough is medium-soft and tacky but doesn't stick to fingers.
Turn dough ball and bits out onto an unfloured counter and gather into a neat ball. If dough feels stiff, wet hands and knead in the water from your hands. Transfer to an oiled bowl. Cover with plastic wrap and let rise in a warm place until nearly doubled, about 45 minutes.
Meanwhile, cut twenty-four 3-inch squares of parchment paper. Put remaining 1 tablespoon oil in a small bowl.
Cut dough in half. Roll one half into a rope, about 1 1/2 inches thick and 14 inches long; cut crosswise into 12 equal pieces. Roll each piece into a ball, then smack it with your palm into a disk about 1/3 inch thick. With a rolling pin, roll each disk into a thin oval, about 2 1/2 inches wide by 4 1/2 inches long. Brush half of each oval with oil, then fold in half to form buns.
Set each bun on a parchment square; transfer to a bamboo or metal steamer tray, spacing about 3/4 inch apart and away from steamer walls. Set any that don't fit in the steamer on a baking sheet. Loosely cover with a kitchen towel. Let rise in a warm spot until about 1 1/2 times the original thickness, 20 to 30 minutes.
Meanwhile, fill a steamer pan or a pot halfway with water; bring to a rolling boil over high heat.
Steam buns over boiling water, 2 trays at a time, covered with lid, until puffy and dry-looking, about 8 minutes.
Cooled buns can be chilled up to 3 days in an airtight container or frozen up to 1 month. To refresh, briefly resteam thawed buns or cover with a damp double layer of paper towels and microwave in 15- to 20-second bursts.
Per Serving: 68 calories;1.9 g fat;
11.2 g carbohydrates;
1.4 g protein;
0 mg cholesterol;
90 mg sodium.