1. In a small saucepan, combine 20 g bread flour and 60 ml water. Cook over medium heat, whisking constantly, until it thickens into a smooth paste. Remove from heat and let cool to room temperature.

2. In a large bowl, combine cooled tangzhong, 320 g bread flour, 40 g sugar, 5 g salt, and 7 g yeast.

3. Add 120 ml warm milk and 1 egg. Mix with a wooden spoon or dough hook until a shaggy dough forms.

4. Knead in 30 g softened butter until the dough is smooth, elastic, and slightly tacky (about 8–10 minutes by hand or 5–6 minutes with a mixer).

5. Place dough in a greased bowl, cover, and let rise in a warm place until doubled in size, about 1 hour.

6. Punch down dough and divide into 9 or 12 equal pieces. Shape each into a ball and arrange in a greased 9-inch square or round pan.

7. Cover and let rise again until puffy and nearly doubled, 30–40 minutes.

8. Preheat oven to 350°F (175°C). Brush tops with beaten egg.

9. Bake for 20–25 minutes, or until golden brown and cooked through.

10. Brush hot rolls with extra butter and sprinkle with flaky salt, if desired. Cool slightly before serving.