This cake is an all-time favourite at German coffee afternoons and children’s birthday parties. For some reason unbeknown to me this cake was not part of my mum’s baking repertoire, so for me it has the air of being something ‘extra special’ that I only got to eat on rare occasions. Of course, now as an adult with my own stash of baking ingredients and kitchen I can eat anything I like and whenever I want to (unfortunately I have to tidy up after myself these days, too). So I made this Donauwelle on a random Saturday afternoon, just because I fancied it. This cake is a tasty combination of buttery vanilla and chocolate sponge laced with juicy morello cherries and topped with a light butter cream and glossy chocolate icing. Morello cherries, also called sour cherries (or Sauerkirschen) in Germany, can be purchased in glass jars in those German bargain basement supermarkets that have sprung up all over the UK in recent years (for all their sins). Fresh or regular tinned cherries are also fine. However, morello are best as their acidity makes for a nice contrast with the sweet sponge and toppings. Traditionally, this cake is baked in a large, square tin and cut it into rectangular servings (if you go for this option double the recipe below). I used a 28cm round spring form for a more ‘festive’ gateaux shape.
For the sponge:
125 g butter
125 g sugar
Seeds of one vanilla pod
2 tsp baking powder
2 tbsp cocoa powder
A dash of brandy, rum or kirsch (or milk if you don’t want to use alcohol)
Half a jar of morello cherries, or one tin of cherries, or two good hands full of fresh cherries
For the buttercream:
125 g butter
250 ml milk
25g corn flour
1 vanilla pod
Finely grated zest of ½ organic lemon and a dash of the juice
For the chocolate icing:
150 g good quality dark chocolate
50 g single cream (double cream or whipping cream will also work)
1 tbsp honey
A knob of butter
Whisk the butter and sugar until light and fluffy. Add the eggs one by one and also the vanilla. Mix the flour with the baking powder and thoroughly fold this into the egg and butter mixture – but do not over-mix. Smooth half of the batter into the greased and floured baking tin (it might seem like there isn’t enough, but it will rise). Add the cocoa powder and alcohol or milk to the rest of the batter, mix, and evenly smooth the dark batter on top of the vanilla layer. Swirl the mix with a fork for a marble effect. Top the batter with the cherries, slightly pushing them down. Bake for about 30 minutes at 175 degrees. Remove from the tin and allow to cool.
For the buttercream mix the sugar and corn flour in a small bowl with a few splashes of the milk. Whisk and make sure there aren’t any lumps. Bring the rest of the milk to the boil with the seeds from the vanilla pod and add pod to infuse, too. When the milk boils pour in the corn flour mix. Bring back to the boil and cook for about 2 minutes, whisking constantly. Discard the vanilla pod and allow this thick custard to cool. In order to avoid a skin from forming you can place a piece of cling film directly onto the surface of the custard. Whisk the butter until fluffy then gradually add the custard until everything is light and creamy. The butter and the custard should be at the same temperature to avoid curdling. Add the lemon zest and juice. Evenly smooth the buttercream on top of the cake and refrigerate.
For the chocolate icing carefully melt the chocolate in a bain-marie or in the microwave at low wattage and in short, 30 second bursts. Make sure the chocolate does not get too hot. Gradually add the cream, honey and butter and stir until glossy and smooth. Wait until the icing starts to firm up (if you refrigerate it this will happen faster), then poor on top of the buttercream and smooth all over the cake with a spatula. You can make a wave-like (Danube waves) pattern with a fork if you like.
The cake will keep for a few days, preferably well covered and in the fridge. I actually think it tastes best on the second day when all flavours have had the chance to mingle. However, it usually doesn’t last for very long...