For the Nutella slices, first prepare the dough.
For the dough, sift the flour with the cocoa and baking powder. Separate the eggs and beat the egg whites with a pinch of salt until stiff.
Cream the yolks with the sugar and vanilla sugar and add the soft chocolate, oil and water.
Fold in the flour-cocoa baking powder mixture alternately with the beaten egg whites. Spread on a baking tray lined with baking paper and bake at 180 °C for approx. 15 – 20 minutes (top and bottom heat).
Allow to cool. For the first cream, beat patisserie cream, cream stiffener and powdered sugar until creamy and stir in Nutella.
Spread the cream on the cooled cake base. For the second cream, mix all ingredients until creamy and spread on the dark cream.
Decorate the Nutella slices with chocolate flakes or chips.