Mix all dough ingredients together until well combined.
Let the dough rest for 30 minutes.
Roll out 10g of room temperature butter and spread it evenly on top of the dough.
Roll the dough for about 10 minutes as shown in the video.
Divide the dough into 6 pieces and shape each piece into a ball.
Press down and flatten the dough, then place 10g of butter in the center. Fold over the edges to enclose the butter and seal well.
Let the dough rise for 30-45 minutes.
Place the filling on top using a piping bag. The topping should have strings as shown.
Relax for an hour, take a deep breath, and reshape the bun if needed. It may look bad at first but it will turn out nicely after baking.
Bake in an oven preheated to 180°C for 20 minutes.
For those who do not like coffee, you can replace the coffee topping with a chocolate one by using the same base ingredients and proportions. Simply add vanilla essence and use 2 tablespoons of cocoa powder instead of instant coffee.