Preheat the oven to 180°C (approximately 350°F). Line two baking sheets with parchment paper.
Whisk the butter with the powedered sugar and the vanilla sugar. Stir in the egg. Mix the flour, ground hazelnuts, baking powder and cinnamon. Add the egg mixture and mix together well. With two small spoons, place small heaps of batter on the baking sheet and top with the sliced hazelnuts. Bake for about 10 minutes until golden brown. Take out, peel off the parchment paper and leave to cool.
Dust with powdered sugar and serve.