1. Mix all the ingredients except unsalted butter to form a smooth dough.
2. Add softened unsalted butter, knead until the dough forms a thin film, shape into a ball, cover with plastic wrap, and refrigerate for 30 minutes.
3. Roll the 150g unsalted butter for folding into a 15*15 square, set aside.
4. After refrigeration, roll the dough into a 15*30 thick sheet. Place the folded unsalted butter in the middle, fold the dough on both sides tightly, and then roll it into a 45cm long sheet. Fold it into three layers, cover with plastic wrap, and refrigerate for 30 minutes.
5. Repeat the folding process for the second and third times. After the third fold, roll the dough into a 15*50cm sheet, then roll it up and refrigerate for 30 minutes.
6. Divide into 6 equal parts, ferment at 25°C for about 2 hours until it doubles in size.
7. Brush the surface with egg wash and bake at 175°C with 4D HotAir for about 16-18 minutes.