For the Nutella cake, first prepare the base. For this, beat the yolks with 25 dag sugar until foamy. Slowly stir in oil and water, add flour, baking powder and cocoa and gently fold in.
Finally, beat the egg whites with 5 dag sugar and fold into the mixture, place on a baking tray and bake (180 °C, top and bottom heat, in a preheated oven, approx. 30 minutes).
For the cream, whip the patisserie and mix with cream stiffener, vanilla sugar and powdered sugar. Spread half of the cream on the baked base.
Stir Nutella into the second half, spread on the white cream and sprinkle with chocolate flakes.