Can't Stop Repeating the Filling Recipe. Quick All-In-One Donut Cake. Soft for Days

Hello everyone, this time I'm making a favorite cake that almost everyone loves. I've been looking for a recipe I've never tried before that's practical, and once I make it, I want to make it six times. Indonesians are so good at making donuts that I'm nervous about posting it, guys.

All-in-One Donuts with One Proofing
Recooked & modified: Vinastar Channel
250 grams high-protein flour
35 grams sugar
4 grams instant yeast (I used 1 teaspoon)
1 gram bread improver (optional).
(I used 1/3 teaspoon or less than 1/2 teaspoon, buy the sachet ones 😊)
2.5 grams salt (1/2 teaspoon salt)
15 grams powdered milk
30 grams butter or margarine
1 egg yolk + cold water = 140-150 grams