Knead the flour, baking powder, sugar, vanilla sugar, chopped butter, egg white and ground almonds into a smooth dough. Form the dough into a ball, wrap in plastic and chill for about 30 minutes.
Roll out the dough on a floured surface until about 0.7 cm thick. Cut out rectangles and place the cookies on a lined baking sheet. Bake for about 12 minutes at 180°C (approximately 350°F). Remove from the oven and let cool.
Mix the powdered sugar, almond syrup and water into a smooth icing. Spread the icing on the cookies. Sprinkle with almonds. Let dry and serve.