Donauwelle

Ingredients

Equipment Needed

• •Rimmed baking sheet, about 30x40cm
• •Fine sieve
• •Electric mixer
• •Small offset spatula
• •Cake comb or fork

Instructions

1. 1

   Drain the cherries

   Tip the sour cherries into a sieve and leave them to drain for at least 20 minutes, then blot them lightly with kitchen paper. Keep the juice for another day, Weggeworfen wird nichts. Dry cherries sink into the batter and make the wave; syrupy cherries float, bleed, and leave the cake damp where it should be tender.

   Jarred sour cherries are not a sin here. They are the preserving larder. The shortcut to refuse is instant cream or packet glaze.
2. 2

   Make the custard

   Whisk a little of the cold milk with the cornstarch, egg yolks, sugar, and vanilla until smooth, then bring the rest of the milk just to a simmer. Whisk the hot milk into the yolk mixture, return everything to the pan, and cook while stirring until thick and glossy. It must boil gently for a minute so the starch loses its raw taste and sets firmly enough to hold the buttercream.

   Spread the custard in a shallow dish, cover the surface directly, and cool it to room temperature. Butter and custard must be the same temperature or the cream splits. That isn't bad luck, that's physics.
3. 3

   Mix the batter

   Heat the oven to 180C and line a 30x40cm rimmed baking sheet. Beat the soft butter, sugar, vanilla sugar, and salt until pale, then beat in the eggs one at a time because the batter holds its air better when each egg is absorbed before the next arrives. Fold in the flour and baking powder with 3 tablespoons milk, stopping as soon as the flour disappears so the crumb stays fine.

4. 4

   Build the wave

   Spread half the pale batter evenly in the tin. Stir the cocoa and 2 tablespoons milk into the remaining batter, then spread the cocoa batter over the pale layer. Scatter the drained cherries over the top and press them in lightly with flat fingers. Do not stir them through. They need to sink from above, pulling the dark batter down into the pale layer as the cake bakes.

5. 5

   Bake and cool

   Bake for 30 to 35 minutes, until the top springs back and a tester comes out with moist crumbs but no wet batter. Let the cake cool completely in the tin. Warm cake melts buttercream from underneath, and then you have pudding on a sponge, not Donauwelle.

6. 6

   Beat the buttercream

   Beat the softened butter until light and smooth, then spoon in the room-temperature custard a little at a time. Add the next spoon only when the last one has disappeared, because a slow emulsion gives you a cream that cuts cleanly and does not weep. Spread it over the cold cake in an even layer and chill for 45 minutes, until firm.

7. 7

   Glaze the top

   Melt the dark chocolate with the coconut fat and a pinch of salt over gentle heat, then let it cool until fluid but no longer hot. Pour it over the firm buttercream and spread it quickly. Comb waves through the glaze with a cake comb or fork while it is still soft, because once the chocolate sets, the Danube has closed for the day.

8. 8

   Chill and cut

   Chill the cake until the glaze is set, then cut it with a knife dipped in hot water and wiped dry between cuts. The warm blade goes through the chocolate without cracking it into the cream. Serve small squares with coffee. Schön ist, was schmeckt.

Chef Tips

• •Use sour cherries, not sweet cherries. The cake already has buttercream and chocolate; the fruit has to cut through that sweetness, or the whole piece goes flat.
• •Do not rush the cooling. Cake, custard, and butter need to meet at the right temperature, because buttercream is an emulsion and it punishes impatience.
• •For a cleaner cut, score the chocolate glaze lightly after it has just begun to set, then chill fully before slicing. The score gives the knife a path and keeps the top from cracking.
• •Keep the reserved cherry juice for drinking with mineral water, soaking another cake, or reducing into a syrup. Weggeworfen wird nichts.

Advance Preparation

• •Bake the cake base and make the custard one day ahead; keep both covered at cool room temperature or refrigerate the custard, then bring it back to room temperature before beating with butter.
• •The finished cake is best chilled for at least 2 hours before serving and keeps well for 2 to 3 days in the refrigerator.
• •Cut only what you need. The uncut slab keeps the buttercream protected and the glaze cleaner.

Frequently Asked Questions

Nutrition Information

1 serving (about 150g)