- Whisk together water, yeast and sugar in a small bowl. Set aside and allow yeast to bloom for 5-6 minutes.
- In a large bowl, combine flour, baking powder and salt, then add yeast mixture and oil. Stir together to form a rough dough.
- Transfer dough to a clean work surface and knead for 8-10 minutes or use a stand mixer with the dough hook fitted to knead. The dough should be sticky, stretchy and smooth. If dough is too dry, add an additional 1-2 tablespoons of water. Coat a medium bowl with a small amount of oil. Add dough to bowl. Cover with a damp towel or plastic wrap and place in a warm location to rise for 1 hour. On top of a warm oven or in a sunny window will work well.
- Cut 12 squares of parchment paper, 4×4 inches, then place squares on a large baking sheet.
- Punch the dough a few times to release air. Lightly flour a clean work surface and roll dough out using a rolling pin to ¼ inch thick. Cut 3-inch circles of dough using a cookie cutter or a glass.
- Using hands, stretch dough circles into oval shapes. Place ovals onto parchment paper squares and lightly brush with oil, then fold into half-moons. Cover with plastic wrap and let dough proof for 30 minutes longer or until bun size has doubled.
- Working in batches, place the buns on parchment paper in a bamboo steamer basket over a steamer pot filled with 1 inch of water. Cover bamboo basket with lid and bring steamer pot to a low boil. Steam buns for 8-10 minutes. Turn off heat and let buns rest in steamer 5 minutes longer to prevent deflating. Repeat the cooking process with remaining buns.
- While buns cook, heat 1 tablespoon of oil in a medium skillet over medium-high heat for 1 minute. Add chopped chicken thighs and cook for 8 minutes, stirring occasionally for even browning. Reduce heat to medium, add bell pepper, and continue to cook for 2 minutes longer. Stir in teriyaki takumi sauce and lower heat. Simmer for 5 minutes.
- Once all the bao are steamed, gently open them and fill with teriyaki chicken mixture. Top with sesame seeds, cilantro and sliced jalapeño