Heat up milk in a microwave for 30s. It should be hot but not unbearable to the touch. Dissolve sugar and oil and sprinkle yeast on top. Let rest for 5 minutes or until foamy.
Combine together flour and baking powder. Mix flour mixture into the yeast mixture and knead until a smooth and elastic dough forms. Let rest for 1 hour.
Prepare your steamer with parchment paper, steaming cloth/liner.
Make mantous: Using your hand, flatten the dough onto your work surface. Using a rolling pin, roll the dough out into a rectangle. Take one side and tightly roll into a log. Slice into 8 even pieces and place them seam side down in the steamer.
Cover the steam basket and let the dough prove for 30-60 minutes.
Add water to a pot and turn your stove on high. Place the steam basket on top and steam for about 10-12 minutes. Turn off the heat and let the buns sit for about 5 minutes before serving.
Storage: You can freeze the buns once they have cooled. To reheat, just pop it back into the steam basket and repeat the steaming step.