This is a very popular German cake recipe with cherries, vanilla custard and chocolate! The Donau is a river and Welle is the German word for wave.
Unfortunately, my daughter chose this recipe for a German class project. Though I followed the recipe, the 'custard' never got thick enough to spread. I ended up at the 24 hour market getting premade pudding to spread. There was no instruction on when to add the second measurement of vanilla and the chocolate siezed up. She was crying and I was not happy. - 28 Mar 2006 (Review from Allrecipes USA and Canada)
We have edited this recipe and corrected the directions for making the custard layer. The mixture must be boiled for the cornstarch to thicken the custard. We apologize for any difficulties this error created. - 25 Aug 2009 (Review from Allrecipes USA and Canada)
I've made this cake many times but used a different custard. Here is how I made it: Cook 2 packages vanilla pudding but only use the milk for one package. Let the pudding cool down. Take 1 cup of unsalted butter and mix it until it's creamy. Test both the pudding and the butter for the same temperature and slowly mix the cooked pudding, under permanent mixing, into the butter. Let it cool down on the cake before you put the chocolate on it. - 31 Aug 2009 (Review from Allrecipes USA and Canada)