For the buttermilk cake, mix flour, half of the sugar, baking powder, vanilla sugar, eggs and buttermilk in a food processor to a dough.
Line baking sheet with parchment paper and spread batter evenly on it. Mix coconut flakes, cinnamon, the remaining sugar, walnuts and sprinkle over the dough.
Bake at 200 °C for 20 minutes. Immediately after baking, pour whipped cream over the hot buttermilk cake.