Let the butter sit at room temperature until softened.
Add white sugar and brown sugar, then cream together.
Add the egg and mix well.
Sift in cake flour, baking soda, and salt, then mix evenly.
Add chocolate chunks and walnuts, and combine into the dough.
Scoop large portions of dough and roll them into balls.
Place the dough balls on a baking pan.
Bake in a preheated oven at 180℃ for 12–15 minutes.