Mix the flour, sugar and vanilla sugar. Chop the butter into small pieces and add. Add the vanilla flavoring. Knead quickly into a smooth dough. Wrap the dough in plastic and chill for about 30 minutes. Roll out on a floured surface until 5 mm (approximately 1/4 inch) thick. Use cookie cutters to cut out stars.
Place the stars on a lined baking sheet. Bake for about 10 minutes at 180°C (approximately 350°F), until golden brown. Beat the egg white with the powdered sugar until stiff. Pour the icing into a piping bag. Decorate the stars with the icing. Bake for another 5 minutes, remove from the oven, let cool and serve.