In a stand mixer using dough hook, combine flour, sugar, yeast, salt and baking powder. Slowly pour in room temp milk and tablespoon oil. Mix for 10 minutes on low speed until dough is elastic, smooth and soft. (If you find the dough too wet, add 1/2 tbsp flour at a time and knead it in until it reaches a consistency that's not too sticky.) Shape it to a large ball and cover with damp cloth. Set aside for 1 hour to rise.
Cut 10 4-inch square parchment paper squares for steaming.
Punch the dough down and roll out to 1/2 inch thickness, then brush sesame oil over the top. (This will help the baos open up the after being steamed).
Use a cookie cutter or cup to cut 3 1/2 - 4 inch circles out of the dough. Fold each circle in half, place it onto the parchment squares and gently press down to flatten. Cover with kitchen towel and let the baos rest for another 30 minutes (they will rise during this time).
In a wok or steamer boil water and place steamer basket inside. Transfer buns with parchment squares to the steamer with 1 inch room around each. Cover and steam over medium heat for 12 minutes. Turn heat off and leave lid on, let rest 5 minutes.
Remove to rack to cool and repeat with remaining buns.