Boil up red wine, rhubarb nectar, sugar, vanilla sugar, cinnamon, star anise and allspice in a small high pot. Scrape vanilla pulp from the pod. Peel apples. Add the apples, vanilla pulp and pod to the stock and boil for 15-20 minutes.
Remove from the heat, let apples cool in the stock.
Pour the brew through a sieve into a wide pot and reduce to about 100 ml. Stir starch and 1 tbsp. water until smooth, thicken brew. Arrange apples with the stock, decorate with spices if necessary. Serve with vanilla sauce and roasted walnut kernels.