This cake comes from Rick Rodger's wonderful book, Kaffeehaus, about the classic desserts of the famous Eastern European pastry and coffee houses. In addition to recipes, the book is filled with interesting stories about chef's, shops and the great Sachertorte debate. This chocolate mousse cake is named for the famous pastry chef who invented it. The interesting thing about this cake is that the two layers are practically identical in ingredients and proportions, it is the manipulation of the ingredients that creates the marked difference between them. The top layer is not your typical mousse texture; it is rather a cross between mousse and buttercream. The bottom layer bakes up very caky, however there is no flour in it at all.
I won't say this cake is complex, because it isn't once you actually do it. It only looks complex on paper, and is too much to copy down here. So I suggest getting yourself a copy of the book to discover all the wonderful traditional cakes, cookies and pastries.
I serve the cake with a raspberry port sauce.