Chocolate cake: boiling water on the cocoa, and a crumb that stays moist
The commonest problem with chocolate cakes is dryness — cocoa is thirsty and pulls moisture out of the crumb. American recipes have long known the answer, though European books rarely mention it: the cocoa must be bloomed in boiling water before it goes into the batter. Hot water draws out its aroma and lets it disperse evenly, and the cake gains water that the cocoa no longer takes from the crumb. The result is layers still moist on the third day.
Your own work in that: 3 h.
- Layers 60 min
- Ganache 60 min
- Assembly 120 min
Step by step
0 / 6 doneBloom the cocoa in boiling water
Tip the cocoa into a bowl and pour over the boiling water, whisking to a smooth, glossy paste. Set aside to cool. Boiling water draws out the cocoa's aroma and deepens its flavour noticeably — that is the difference between a cake that is chocolate-flavoured and one that tastes of chocolate.
Ingredients: 280 g plain flour · 80 g dark cocoa · 240 ml boiling water · 320 g sugar · 3 pcs eggs · 150 ml rapeseed oil · 240 ml buttermilk · 2 tsp baking powder · 1½ tsp bicarbonate of soda · 1 tsp salt
TipHot coffee instead of water works better still. It gives no distinct coffee flavour but deepens the chocolate — a well-known pastry trick.
Boiling water on cocoa, a glossy pasteMix the batter
In a large bowl combine the flour, sugar, baking powder, bicarbonate and salt. In another whisk the eggs with the oil and buttermilk, then add the cooled cocoa paste. Pour wet into dry and whisk only until combined. The batter will be very loose, almost like pancake batter — as it should be.
TipDon't try to thicken it with flour. That looseness is the reserve of moisture that stops the layers drying out after two days.
A very loose batter, almost pourableBake two layers
Divide the batter between two 22 cm tins lined with paper and bake in an oven heated to 175 °C for 35 minutes. A skewer should come out with moist crumbs. Cool in the tins 15 minutes, then on a rack until completely cold, ideally overnight.
Thirty-five minutes, moist crumbs on the skewerMake the ganache
Chop the chocolate finely into a bowl. Bring the cream to the boil and pour it over, wait a minute without stirring, then stir from the centre outwards until smooth. Stir in the butter. Leave 60 minutes at room temperature to thicken.
Ingredients: 400 g dark chocolate, 60 % · 400 ml whipping cream (30%) · 40 g butter
TipThat minute without stirring is not superstition: the hot cream must first warm and soften the chocolate. Stirred at once, it cools faster, leaves lumps and is more likely to split.
A minute untouched, then stir from the centreSplit and soak the layers
Cut each cake horizontally in half with a long knife — you get four thinner layers, of which you use three (freeze the fourth for another day or crumble it for decoration). For the syrup, boil the water with sugar and coffee, cool it and brush 3 tablespoons onto each layer.
Ingredients: 100 ml water · 2 tbsp sugar · 1 tsp instant coffee
Assemble and coat
Sandwich the layers with ganache, 4 tablespoons per layer, levelling with a palette knife. Coat the top and sides with the rest. Refrigerate an hour for the ganache to set. Take it out 30 minutes before serving — a cold cake has a dense crumb and muted flavour.
Four spoons per layer, then an hour chilling
Before you start
Why oil, not butter
Butter hardens in the fridge, so a butter cake seems dry when cold. Oil stays liquid even at low temperatures, so the layers are moist straight from the fridge. That is why so many American chocolate cakes are made with oil.
Without buttermilk
Instead: 240 ml of milk plus a tablespoon of lemon juice, left 10 minutes. The acid matters — without it the bicarbonate cannot react fully, the layers rise noticeably less and may taste soapy.
Ganache too thin
Put the bowl in the fridge for 20 minutes and stir. If it is still runny, add 50 g of melted chocolate. Too thick is rescued by a spoon of warm cream.
How long it keeps
Four days in the fridge under a dome, a long time for a layer cake. The ganache acts as a seal and stops the layers drying.
