In a bowl, stir together the flour, caster sugar and almond meal. Rub in the butter to form crumbs, then stir in the egg yolks and work into a smooth dough. Wrap in plastic wrap and chill in the fridge for 1 hour.
Preheat the oven to 180 degrees C.
Roll biscuit dough into long snakes. Cut into 5cm lengths and shape each length into a crescent. Place on a baking tray lined with baking paper.
Bake in preheated oven until lightly golden, about 10-15 minutes.
Immediately roll the biscuits in vanilla sugar while still hot, then set aside to cool.