For the crumb cake, separate eggs and beat egg whites with a little salt until stiff. Chill. Beat the egg yolks with the sugar until foamy, then add the orange zest.
In a weidling put the flour, mix with baking powder, then add cocoa and cake crumbs and chocolate, mix well. Now add the egg yolk mixture and beaten egg whites, as well as oil and cinnamon and gently fold everything in.
Pour into a greased cake pan (26-28 cm or a Rein) and bake at 180 degrees top/bottom heat for about 45 minutes. Serve while still warm with whipped cream and, for example, blackberry dessert sauce.