In the bowl of an electric mixer with a dough hook attachment (you can also knead by hand in a mixing bowl), dissolve the yeast in the warm water. Sift together the flour and cornstarch, and add it to the yeast mixture along with the sugar and oil. Turn on the mixer to the lowest setting and let it go until a smooth dough ball is formed (approximately 2 minutes). Cover with a warm, damp cloth and let it rest for 2 hours. 

While the dough is resting, make the Adobo.

Heat the olive oil in a dutch oven or similar pot over medium high heat. Add the chicken and brown in batches, removing the chicken once browned. Turn heat down to medium and sautée the garlic until golden brown. Add the chicken and its juices and the rest of the ingredients. Bring to a boil then simmer over medium-low heat for 1 1/2 hours.

After your dough has rested for 2 hours, add the baking powder to the dough and turn the mixer on to the lowest setting. Gently knead the dough until it becomes smooth again (approximately 1 minute). Cover with a damp cloth and let it rest for another 15 minutes. In the meantime, cut parchment paper into ten 4x4 inch squares. Prepare your steamer by bringing the water to a boil.

Roll the dough into a long tube and divide it into 10 equal pieces. You can also weigh the dough and divide it equally that way.Press each piece of dough into a disc about 5½ inches in diameter (it should be thicker in the center and thinner around the edges). Add some filling and pleat the buns until they're closed on top.

Place each bun on a parchment paper square, and steam for 15 minutes over high heat. I steamed the buns in several batches.