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

Cook over low heat, stirring constantly.

When the mixture thickens and shows lines (around 65°C / 150°F), remove from heat.

Cover and let it cool.

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.