Siopao (Filipino Steamed Dumplings)

In a bowl, dissolve yeast in warm water, then mix in sugar and 2 1/2 cups of rice flour to form a soft sponge. Set aside in a warm place to double in size, about 40 minutes. Add 2 more cups of rice flour and 1/4 cup shortening. Transfer dough to a greased surface and knead in the remaining shortening until smooth. Divide the dough into 15 equal portions and shape each into a ball.

Heat vegetable oil in a skillet over medium heat. Cook onion and garlic in the oil until translucent, about 5 minutes. Add chicken, soy sauce, 2 teaspoons sugar, green onion, salt, and pepper. If the mixture is too watery, add cornstarch to thicken it.

On a lightly greased surface, flatten each dough ball into a 4-inch circle. Place 1 tablespoon of the chicken filling in the center of the dough, fold the edges up to enclose the filling, and pinch and twist to seal. Place the filled dumplings seam-side down on wax paper and repeat with the remaining dough.

Coat a multi-layered bamboo steamer with cooking spray, then place it over a large saucepan filled with water just below the steamer. Bring the water to a boil.

In batches, arrange 3 to 4 filled dumplings in each layer of the steamer, ensuring they do not touch. Cover and steam over medium-low heat for about 15 minutes per batch, or until the dumplings are puffed and the dough is springy. Serve warm.