Preheat oven to 180 C / Gas 4 and line a baking tray with parchment.
In a bowl combine flour, baking powder and salt. Add butter, 50g sugar and egg and knead into a smooth dough. Mix in chocolate chips. Divide into 12 portions, roll into little balls and place on the baking tray.
Bake for 15 minutes in the preheated oven. Mix 1 tablespoon sugar and vanilla sugar on a plate. Dredge biscuits in the sugar while still hot and set aside to cool.