Is it similar to this?
http://awayofmind.blogspot.com/2017/07/creamy-custard-bread-65c-tangzhong.html
That’s as close as I’ve seen. I’m wondering if they just brushed the bread with pastry cream before baking. Since it was in different dinner roll type shapes there would be places for the cream to gather.
I wish I had paid a bit more attention.... but alas I was only 16 and basically in a teenage fog.
I may have to experiment!