Beat eggs and powdered sugar until frothy. Mix the pudding powder, baking powder, cocoa and hazelnuts and fold in. Pour into a springform pan lined with baking paper.
Bake in the preheated oven at 175 ° C for about 40 minutes. Let cool well on a wire rack.
Then hollow out the cake, leaving a rim and a thin base. Crumble the rest of the cake.
For the filling, whip the cream with vanilla sugar and cream stiffener until stiff. Fold in the chocolate flakes and 1/3 of the crumbs. Pour the mixture onto the cake base like a ball, sprinkle the remaining crumbs on top. Dust the molehill with powdered sugar.