I used my go to Hokkaido bread https://www.britishbornchinesefood.co.uk/hokkaido-bread/
I use 70g of raw dough per bao.
The cookie top as below:
Cookie top for 8
57g Salted Butter ( I used unsalted)
1 Egg Yolk
100g Sugar
94g Plain Flour
2 1/2 TBSP Custard Powder
1/4 tsp Baking Powder
Cookie Top 6
43g Salted Butter ( I used unsalted)
3/4 Egg Yolk
75g Sugar
70g Plain Flour
11g Custard Powder
1/4 tsp Baking Powder
Cookie Top 4
22g Salted Butter ( I used unsalted)
1/2 Egg Yolk
38g Sugar
35g Plain Flour
7g Custard Powder
1/8 tsp Baking Powder
You mix all the ingredients together for cookie top and bind with the egg yolk and a drop of milk if you find the yolk is not quite enough to bind it all. You want the mixture to just come together and not too wet. Wrap in clingfilm and put it in the fridge whilst bread is completing first proof. I find this cookie top provides a rich buttery and crispy outcome. After the first proof, shape the dough, let it proof 15 mins before adding the cookie top. Proof another 20 to 30 mins, egg wash before baking. Do not skip the egg wash.