Chill bowl and blade of a food processor in refrigerator. Sift icing sugar and flour, then blend with butter in food processor until mixture resembles breadcrumbs.
Add egg yolks and scrape in seeds from vanilla bean, then blend until dough just comes together. Wrap dough in plastic film and refrigerate for 2 hours.
Roll dough out on a cold, floured surface until 5 mm thick, then