Preheat the oven to 175 C, line a baking sheet with baking parchment, and set it to one side.
Whisk the butter until creamy and then add the icing sugar and salt, mixing well. Add the vanilla sugar, cornflour and desiccated coconut.
Continue mixing at low speed while adding the flour a little at a time, until you have a smooth batter.
Roll the batter into balls (1 tbsp of batter for each), place on the baking sheet and bake for 16-18 minutes.
Remove balls from the oven and leave to cool for a few minutes before rolling in plenty of icing sugar. Place them on a wire rack and leave to cool fully.
Roll the balls in icing sugar again just before serving.