Preheat the oven to 170°C (338°F).
Put the butter in a bowl and soften it.
Add sugar and salt and mix well.
Add the egg and mix.
Sift in cake flour, cocoa powder, and baking powder.
Add chocolate chips and fold with a spatula.
Shape the dough into balls and place them on a baking sheet.
Bake in the 170°C oven for 12–15 minutes.