Full credit for this cake has to go to Smitten Kitchen. It turned out amazing, as all Deb's recipes do, and is the perfect tea-time/Kaffee und Kuchen cake to serve!
I slightly tweaked her recipe by using a mix of quark, sour cream and mascarpone in place of the 2 cups of sour cream. You can find the recipe here. Take my advice and try it out. :)