In another bowl mix together egg yolk.sugar.cornflour then slowly add in the little of the warm milk and mix well until combined.then strain it to the remaining milk and cook until its thick and creamy.
Add to the clean bowl and wrap with cling wrap and Chill until use.
To make Bun
Mix Together Flour,milk powder,salt,sugar,yeast, then add in the beaten Egg,,warm milk knead well.when its mixed well add in the Soft butter and knead to soft dough and keep aside for 2 hrs.
When its doubled in size punch it back and seperate them into small balls .
ROLL Each balls and fill it with tbsp of custard ,make them into round balls and keep aside for 30 minutes.
Brush the pan with butter then layer with parchment paper Then keep the buns and cook both sides 6 minutes each.