This popular traybake is so wrong, and on so many levels, that it simply has to be right. It has everything you’d expect from a cake: it’s pretty, delicious and it contains every ingredient you’ve ever been warned about. And in double quantities. Its German name is ‘Waves of the Danube’, probably because of the beautiful wavy pattern of the sponge base: 
Why Danube? Nobody quite knows why. Nor why in some areas it is called ‘Snow White’s Cake’, either. But regardless, it makes for a stunning show stopper kind of cake that is easy enough to make but takes quite a while as the different layers need to cool down and set before you can attempt to add the next one.
The base of the cake is a simple sponge, similar to a marble cake, as half of it is dyed with cocoa powder. The waves are created by soured cherries that sink into the cocoa layer. The cake is finished off with a layer of buttercream and crème pâtissière, topped with chocolate couverture – sweet and sour, juicy and rich, with the subtle bitterness of the couverture to round it all off. Some people use ready-made custard instead of homemade one, which is shocking but an option. I’ll leave it up to you. I used a recipe by the Austrian chef Johann Lafer, who has a popular cookery show on German TV. Of all the recipes out there in cyberland, his is the only one that doesn’t use custard powder, and I admire him for it. If this hasn’t convinced you because you’re worried about the calorie count, you can easily work it off by vigorous waltzing, for example to Strauss’ famous ‘Blue Danube’ … 
Donauwellen Traybake (for a 25×30 / 10×12 in baking tray)
For the sponge:
- 300g soft unsalted butter
- 250g caster sugar
- 5 eggs
- 400g plain flour
- 1 tsp baking powder
- 1 pinch of salt
- 3-4 tsp cocoa powder
- 2 tbs milk
For the filling:
- 650g jar of sour cherries, drained
For the buttercream layer:
- 500ml full milk
- 1 vanilla bean
- 4 egg yolks
- 80g sugar
- 4 1/2 tbs corn starch
- 180g unsalted butter
For the couverture:
- 100ml double cream
- 25g unsalted butter
- 70g milk chocolate couverture, in small chunks
- 80g dark chocolate couverture, in small chunks
Preheat the oven to 180C / 360 F. Line the baking sheet with parchment paper. I used two smaller pyrex dishes, which is less pretty, I think, but allowed me to take half the cake to work. Beat the butter and sugar in a bowl until foamy, which takes about 5 minutes with an electric mixer. add one egg after another, mixing it in before adding the next one. Finally add the flour, baking powder and salt and mix it in.
Pour half the batter into the tray and spread it out evenly, using a scraper or similar. Mix the cocoa powder and the milk under the remaining half of the batter, then spread it evenly on top of the first half. Distribute the drained cherries evenly over the mix.
Bake for 25-30 minutes, then remove the tray from the oven and let it cool completely. Now prepare your crème pâtissière or custard. Pour the milk into a medium saucepan. Slice the vanilla bean open and scrape out the seeds, adding them to the milk, which you then bring to boil. Set it aside to cool down a little. You can place the cleaned-out pod into a jar filled with caster sugar: in a fortnight ‘s time you’ll have the most deliciously scented vanilla sugar and you can use the dried-out pod for another batch of custard, simply infusing it in the milk for 20 minutes or so after boiling it. Beat the egg yolks with the sugar until white and creamy (this will take a few minutes). Add the corn flour, then the warm milk. Mix it well before bringing it back to boil. You need to do this slowly, stirring it all the time. Once it starts bubbling, remove the pot from the heat and pour the custard into a bowl or similar.
Leave the custard to cool down. To prevent it from forming a skin, keep stirring it regularly. The custard needs to be completely cool before you can start making the buttercream.
Once both the sponge and the custard are completely cool, you can beat the soft butter, using an electric mixer. When it is completely light and fluffy, add the custard, one tablespoon at a time. When it is all mixed, spread the buttercream in a neat layer over the sponge and place it in the fridge for at least 2 hours.
After the two hours it is time to make the chocolate couverture. In a medium saucepan, bring the cream to boil. Once it is bubbling wildly, add the butter and remove the saucepan from the heat. Stir it to meld down the butter, then add the chocolate. Mix it all until the chocolate is fully melted, then spread it on top of the custard layer. Decorate it with a fork.
Leave it to harden, ideally for a day or so. To cut it into neat slices, heat up your knife in hot water but dry it before cutting through the frosting. 
Enjoy with a cup of tea or coffee. Or simply head over to Angie’s Fiesta Friday party, which is always a great place to start the weekend! This week she’ll be helped by Dini @ Giramuk’s Kitchenand Mollie @ The Frugal Hausfrau, who are co-hosting the event. But if it is all too indulgent for you, why not check out my strawberry cheesecake recipe instead? Either way, you’d better hurry, or there’s nothing left but one lucky cherry stone …
Ginger&Bread 
Looks amazing and I could just dive into that custard! We have a fiesta this weekend in a local village, mostly the music is paso dobles but there’s usually a waltz or two as well, so I shall dance the waltz and think of you and this cake!!
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You’d have to do quite a lot of waltzing to work off this calorific equivalent of a H-bomb … As for paso doble, that always reminds me of Strictly Ballroom … Enjoy the fiesta!
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I missed the butter in your butter-cream? And can you believe that I neber made this cake before? Some kind of prejudice, maybe- but when even the great Lafer bakes it I will have to also.
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You’re right – it proves that either I am in denial about the sheer unhealthiness of this cake, or I am careless. I leave it up to you to decide … It is a cake to impress, really!
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My “philosophy” calls more for less sugar, fat-reducing is neither so important nor that healthy as widely believed.. maybe for the weekend I’ll give it a try.
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What size should the tray be?
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Lafer suggests 25×30. I used two pyrex forms instead, 25×18 and 22×15 or thereabouts. I hope that helped! Enjoy 😉
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thank you- I’ll take out my ruler….
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This cake is to die for…..it looks so deliciously moist and sweet with those ingredients, I like the addition of the sour cherries, and I absolutely love the tines of the fork finishing off the frosting. Just perfect!
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That cake does have it all. Thanks for sharing with us.
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A slice of this cake mimics the graceful dancers with its undulating layers of vanilla and chocolate…plus the cherry surprise! OMG divine!
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I wish that empty plate was mine, or maybe I wish that the full plate was mine! Gorgeous cake and it sounds delicious!
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This cake looks amazing! With sour cherries it must be to die for!
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Simply beautiful photography and I wish you had snuck some of this in your bag yesterday for us lol. Your descriptions are amazing and make me super hungry but it looks difficult lol. However even as I fear difficult looking puddings I’m seriously tempted to try this. Lovely to meet you yesterday 😀😀😀
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This is my first time to hear this cake. It sounds delicious. 🙂 Happy FF!
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I’ve always wondered what exactly is in this cake – thank you for the clarifications! The ones I’ve seen in cake counters have always looked a bit dry but yours, of course, looks extremely tempting!
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Happy FF! I love the last photo – it just says it all. What a glorious cake! We have Boston Creme Pie here which is a little simpler, no cherries and topped with a chocolate glaze. It reminds me a bit of this recipe. Sponge with a layer of custard in the center.
I know this is absolutely worth the labor of love – I’m also glad it doesn’t use custard powder which isn’t readily available here!
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It looks so cool!!
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What a cake… What a cake!!
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this looks exceptional – talk about a stunning dessert.
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How amazingly beautiful is this cake?? It is definitely a show stopper! I love the wavey pattern in it and can see why it is named after waves! I’ve never had Sweet danube before and now I really really want to make it! Absolutely gorgeous Ginger! 😀 Happy FF!
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Gosh this looks fabulous! I love how the cherries sink, causing the waves – very clever! Where do you get your sour cherries from?
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Only the most exclusive Delis in London stock them, such as Lidl and any of the little Eastern European shops 😉 I get them in large glass jars and my recipes are usually made to use up one jar (but not the syrup … that would be too much sugar …)
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I’ve seen them in Lidl but they look a very bright pinky red – must see if they have anything else in. We also have a few EE shops so will take a look – thanks x
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Don’t use glacé cherries or whatever they are called – they are indeed very pinky red! I buy Lidl’s ‘Harvin’ brand, ‘cherries in syrup’. 680g with and 350g without the syrup. They are sour cherries, or morello cherries, which we use fir many different cakes to get a nice acidic note to an otherwise sweet dish. Good luck finding them!
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I once had to make a packet mix of this cake at the insistence of a small child of mine who had won it in a raffle… I have to say, I much much much prefer the sound (and look!) of yours! 😀
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I’m afraid, my only attempt at a packet mix (Betty Crocker’s Brownie Mix) Was so disastrous that people still talk about it – 12 years later!
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This is too awesome not to try!! Would fresh sour cherries work in this?
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I’m sure they would! We used to have lots of sour cherry trees when I was a kid, and my mum preserved the fruit by making endless jars of compote, similar to the one I used, as they are perfect for preservation. But the real thing must be even better!
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Will definitely go picking then! In a few weeks sour cherry season starts. I must make a note not to forget!! Thanks, Ginger!
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My Goodness Ginger this cake looks divine!! We have something similar- my sister makes it, I’ve never attempted it, but THIS one here is a masterpiece!
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This looks heavenly! Yum!
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Thanks, Indu!
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Oh yum, mouthwatering 😉
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Thanks for the recipe <3, will come back and let you know the outcome of how my own went.
have a lovely day
What men secretly want lady
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I am too excited! I hope it works out alright!
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made this yesterday to great applause… ebven if I found the base a bit too firm. I used a bio-Weinstein- baking pwder and will try again with the regular viariety. And will make a photo at least I hope I won’t forget my camera… great recipe!
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This looks so amazing. I have never tried anything like this before! What a combination of textures and flavors!
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