Sift the flour, salt, baking powder, and cornstarch, then mix together.
Mix the brown and white sugar with the melted butter.
Add the egg and continue mixing.
Pour the wet ingredients into the dry ones and mix until a dough forms.
Add the chocolate to the dough and refrigerate for at least 3 hours (you can even freeze the dough and bake the cookies whenever you want).
Shape the cookies as desired.
Make sure they are tall enough to keep their shape after baking.
Bake for 15 minutes at 180 °C.
The cookies may seem underbaked or too soft — this is normal. Let them cool on the baking tray at room temperature, then enjoy with fresh milk or a cappuccino.
