Using a whisk, combine all the ingredients and bring to the boil over a medium heat, stirring constantly. As soon as the mixture thickens and turns creamy, remove the pan from the heat and continue whisking for approx. 2 mins. Pour the crème into a bowl through a sieve, allow to cool, then cover and refrigerate for approx. 2 hours. Stir the sauce until smooth shortly before serving.
Using the whisk on a hand mixer, mix the butter, icing sugar, vanilla sugar, salt and water in a bowl until the mixture becomes fine and crumbly. Stir in the flour, beat briefly and form a dough. Place the dough in a plastic bag, press down firmly, refrigerate for approx. 30 mins.
On a lightly floured surface, shape the dough into a rectangle approx. 4 mm thick, chill for approx. 30 mins. Transfer the dough to a baking tray lined with baking paper. Cut out the chips (approx. 1 cm x 8 cm), use a dough scraper to push them apart a little.
Approx. 12 mins. in the centre of an oven preheated to 200°C.
Chocolate cookie French fries
Place the chocolate in a thin-sided bowl and suspend over a gently simmering bain-marie, ensuring that the bowl does not touch the water. Melt the chocolate. Dip half of the cookie French fries into the chocolate, leave to dry on a rack.
Serve the cookie French fries with the vanilla sauce.