Sift bread flour and cake flour into a bowl, then add sugar and salt.

Mix the dry ingredients evenly with a whisk.

Add cold butter cut into 1cm cubes.

Use a scraper to chop and mix the butter into the flour.

Create a well in the center and pour in the egg yolk mixed with cold water.

Combine the ingredients lightly until the dough starts to come together.

Wrap the dough and refrigerate for 1 hour.

Roll the dough into a long rectangle in one direction.

Fold the dough into thirds (letter fold).

Rotate the dough vertically, roll again, and repeat the folding process three times.

Refrigerate the folded dough for 1 hour.

Roll the dough into a long rectangle again.

Fold the top and bottom edges inward by 1/6 of the length.

Fold the dough in half along the center.

Refrigerate the folded dough for 30 minutes.

Slice the dough into 1cm thick pieces.

Coat one side of each piece with sugar.

Place the pieces on a baking tray with enough space between them.