Preheat the oven to 180 C / Gas 4. Line a baking tray with a silicone sheet or baking parchment.
Mix the butter, caster sugar, dark brown soft sugar and vanilla sugar in the bowl of an electric mixer on low speed until creamy. Add the eggs and continue to mix on low speed until homogeneous.
Leave the mixer on low speed, and add the flour and baking powder gradually until all ingredients are moistened. Stir in the chocolate chips. (Now, even though the dough is ready - you do not need to eat all of it yet!)
Drop 5cm balls of the cookie dough onto the prepared baking tray.
Bake in the preheated oven until golden at the edges, about 15 minutes. Let cool on the baking tray for 5 minutes, then remove to cool completely on a wire rack.
My nieces prefer these cookies a little soft, but if you prefer them a little crunchy, bake for 20 minutes.