Mix flour and milk in a saucepan, whisk until smooth.

Cook over low heat, stirring, until thickened (≈65°C), then cool.

Mix bread flour, sugar and salt.

Add milk, egg and tangzhong.

Knead into rough dough, chill 4 hrs or overnight.

Mix yeast with a little milk, add to the dough, and knead until smooth.

Add softened butter and knead until elastic.

Cover and ferment until doubled.

Divide to 3 balls, shape into logs and place in loaf pan.

Proof until 80–90% full. Brush with egg yolk + milk.

Bake at 170°C for 30–35 min.

Take out the loaf from the oven and remove from the pan.

Brush top with butter to keep it soft and shiny.