For the cookies, mix the flour, brown sugar, vanilla sugar, salt and almonds on the work surface and mound up into a pile. Make a well in the center and scatter the butter in small pieces over flour. Add egg to well and chop ingredients together (preferably with a dough scraper) until coarse crumbs form. Quickly knead into a smooth dough. Add a little flour or cold water as required. Wrap in plastic wrap and let rest for about 30 minutes in the refrigerator.
Preheat the oven to 175°C (approximately 350°F). Line baking sheet with parchment paper.
Roll out the dough in portions 2-3 mm (approximately 1/8–1/4-inch) thick and cut tree shapes in different sizes. Place on the baking sheet. To decorate, sprinkle some with hazelnuts. Bake in the oven until golden brown, 10-12 minutes. Carefully remove from the baking sheet, roll some of the cookies in brown sugar while still warm and allow all to cool on a wire rack.
To decorate remaining cookies, blend powdered sugar with the lemon juice to a thick icing. Top some of the trees with the icing and cover with the pine nuts.