: chocolate sheet:

20g cake flour
50g sugar
1 egg white
80ml milk (warmed)
18g cocoa powder
10g butter

1. Mix sugar and cake flour into the egg white until smooth.

2. Place milk in a saucepan and heat till just simmering.

3. Add coca powder into the milk and stir till cocoa powder is incorporated into milk.

4. Add egg white mixture into the cocoa mixture and stir over low fire till mixture thickens and form a thick lump.

5. Add in butter and stir till incorporated.

6. Leave to cool. Place in a plastic bag and roll into a square. Keep refrigerated before use.

:Banana dough:

In a large bowl, combine everything except butter. Beat until well blended using a stand mixer with a dough hook attachment.

Add in butter and knead until dough is smooth and elastic. Shape into a ball. Place dough in a greased bowl. Cover, and let rise in a warm place for 60 minutes (2.5~3 times larger in size).

After rising, roll the dough into a ball. Let rest for 25 minutes.

Roll out the dough into a rectangle (2:1). Place the chocolate sheet on the middle of the dough. Wrap both ends of the dough over to cover the chocolate sheet completely. Seal the edges tightly.

Gently roll dough from center to the edges to form a long rectangle. Fold the dough into 3 folds. Cut into 2 long stripes. Twist both ends with different direction to from the swirl. Seal the ends underneath.

Let rise for 50 minutes or until 1.5~2 times larger in size. Brush egg wash on the top.

Bake 200C/392F for 40 minutes. You may need to leave a small gap in the oven door to prevent over baking the top. (I opened the door in last 10 minutes, the top is browned, but did not burn)