Mix bread flour and milk in a saucepan, whisk until smooth and no lumps remain.

Cook over low heat, stirring constantly to prevent burning.

When the mixture thickens and distinct lines appear in the paste (around 65°C / 150°F), remove from heat immediately.

Transfer to a clean bowl. Cover with plastic wrap touching the surface to prevent a skin from forming. Let it cool completely before using.

In a mixing bowl, combine milk, egg, sugar, salt, yeast, and Tangzhong.

Add flour and mix until dough roughly comes together.

Add butter and knead until smooth and elastic.

Cover it and let rise until doubled in size (about 1 hour in a warm place).

Punch down dough and divide into equal portions.

Shape into balls and let rest for 10 minutes.

Roll each piece, wrap around a sausage, and place on a baking tray.

Let rise in a warm, humid place until 1.5 times bigger (about 40 minutes).

Brush with egg wash.

Preheat oven to 170°C.

Bake 15–18 minutes until golden brown.