1. Combine bread flour and whole milk in a saucepan. Cook over medium heat while stirring until a thick paste forms. Remove from heat and transfer to the stand mixer bowl.

2. Add cold milk to the tangzhong to cool it. Add sugar, yeast, milk powder, salt, egg, and bread flour. Mix using a dough hook on medium speed for 12–15 minutes until dough is smooth and elastic.

3. Add softened butter and continue to mix for 5 minutes. Dough should be smooth, elastic, and pass the windowpane test.

4. Transfer dough to a greased bowl, cover with plastic wrap, and let rise in a warm place for 1½ hours or until doubled in size.

5. Turn out dough onto a lightly floured surface. Divide into 9 equal pieces (about 90g each). Flatten, tuck into a ball, then roll tightly with cupped hand.

6. Let dough balls rest for 10 minutes. Re-roll each ball to tighten. Place in greased rings or spaced apart on parchment-lined baking sheets.

7. Cover buns loosely and let rise for another 1½ hours until doubled. Preheat oven to 360°F / 185°C about 20 minutes before baking.

8. Brush tops of buns with egg wash. Bake for 15–18 minutes until golden brown. Remove from oven and rings if used.

9. Cool buns on tray for 10–15 minutes, then transfer to wire rack. Let cool completely before serving or storing.