Chocolate Swirl Steamed Buns 巧克力饅頭

Ingredients
Makes 8 buns

• 270g warm milk
• 1 1/4 tsp active dry yeast
• 500g all purpose flour
• 30g sugar
• 2 tsp vegetable oil
• 2 1/2 tsp baking cocoa

Method

1. Dissolve the yeast in warm milk in a large bowl.
2. Mix all ingredients except baking cocoa with yeast mixture until all is blended.
3. Knead the dough until it's smooth, around 5 minutes. 
4. Let the dough rest for 5 minutes in the bowl. Cover it with plastic wrap or a lid.
5. Divide the dough into 2 parts, one 455g and the other 355g dough.
6. Add baking cocoa to the 355g dough, and knead the dough until well blended--cocoa dough
7. Roll out the 455g dough to a  14" x 8" rectangle--white dough 
8. Roll out the cocoa dough to a slightly smaller rectangle than the white dough.
9. Brush the surface of the white dough with water, then place the cocoa dough on top of the white dough.
10. Press the 2 layer-dough gently with your finger, then brush the surface of the cocoa dough with water.
11. Roll out the dough tightly from the longer edge to form a  20" long log.
12. Slice the log into 8 pieces. 
13. Place the buns on the square baking papers. (cut the parchment paper in squares slightly bigger than the buns.)
14. Spread the buns on the steamer and pour some warm water in the bottom of the steamer. Cover the steamer, and let the buns rise for 20 minutes. 
15. After the final rise, turn on the steamer and steam the buns for 20 minutes until it's cooked. 
16. Serve immediately.