Mix the butter, sugar, vanilla sugar, vanilla, egg yolks and salt together until creamy.
Mix in flour and baking powder little by little and knead into a dough.
Roll out the dough about 3 mm thick on lightly floured surface. Cut out into desired shapes, place cookies on the baking sheet and bake in preheated oven (200°C) (approximately 400°F) for about 10 minutes. Remove and allow to cool slightly.
Mix together powdered sugar and lemon juice until smooth. Place icing on the cookies. Optionally, using a small piping bag to decorate and sprinkle with sugar.