Chocolate, coffee, and hazelnut chiffon cake

Chocolate, coffee, and hazelnut, definitely a flavour combination you should try. I made this chiffon cake for my son's birthday, I wasn't planning to post to it, but after many requests, here it is. It's a slightly tweaked, more flavourful version of the nutella chiffon I made for him a couple of years ago, stronger on the coffee, with a good dollop of nutella in the sponge.

We barely made it to the restaurant on time, so there's only a couple of images, check my instagram highlights for the waiter's thumbprint! One of my favourite things about this cake is the nutella swiss meringue buttercream, it's just the right combination of hazelnut and chocolate with a hint of salt, I want to put it on all the things...

chocolate chiffon

200g cake flour
30g cocoa powder
5g baking powder
1/4 tsp bicarb soda
1/2 tsp salt
250g caster sugar
180 ml hot black coffee
60g nutella
125 ml canola oil
1 vanilla bean, seeds scraped or 1 tsp vanilla paste
6 eggs, separated
1 extra egg white
1/2 tsp cream of tartar (not essential, but will stabilise the egg whites)
50g caster sugar

nutella swiss meringue buttercream, recipe below
cooled nutella ganache, recipe below
ferrero rocher, hazelnuts and as much foliage as you like, to decorate

serves 16

• preheat your oven to 170ºC
• add the nutella to the hot coffee, mix to combine and set aside to cool (I made my coffee with 2 strong coffee pods)
• combine the cake flour, cocoa, baking powder, bicarb soda and salt, sift into a the bowl of a stand mixer, if you have one, and with the paddle attachment mix through the 250g caster sugar 
• make a well in the centre of your flour mixture, add the cooled coffee, egg yolks, oil and vanilla extract, mix until smooth
• in another, really large bowl whisk the 7 egg whites until foamy, add the cream of tartar then mix until you have soft peaks, gradually add the additional 50g caster sugar, whisking until you have firm peaks and the sugar has dissolved
• fold the egg whites into the batter in three stages
• pour the batter into an ungreased, unlined angel food cake tin and bake for 55-60 minutes; check after 55 minutes, the cake should spring back when gently pressed, if not, put it back in for the extra 5 minutes
• remove the cake from the oven, and immediately invert to cool; if your tin doesn't have "feet" balance the upturned tin over a bottle, guiding the neck of the bottle through the centre tube of your pan
• when completely cool, to release the cake, run a sharp knife around the inside and tube sections of the cake tin, remove the cake leaving it sitting on the centre section of the tin; this next stage is tricky, slide a strong thread, I use dental floss, between the base of the cake and the tin, slide the string all the way around the cake, crossing each end around the tube. Invert the cake onto a turntable if you have one, or your serving plate, and put in the fridge for 15 minutes or so.

• frosting step one is the crumb coat, it uses a super thin coating of frosting to glue any loose crumbs to the cake
• starting from the top and working your way down the sides and into the hole through the centre of your cake, use an offset pallet knife to spread a layer of buttercream over your cake;  using the edge of your pallet knife or a cake scraper, gently scrape back as much of the frosting as you can leaving a super thin crumb filled layer behind
• return the cake to the fridge for at least 15 mins to set the crumb coat
• again with the offset pallet knife, cover your cake with a final thicker layer of frosting and return to the fridge for at least 15 minutes, this will firm up the frosting and help the ganache set 
• carefully pour the ganache over the top of the cake, you may need to encourage it over the sides, allow to drip, return to the fridge to set
• decorate with ferrero rocher, hazelnuts, and foliage of your choice
• slice giant slabs of cake with a serrated knife and enjoy
• the cake will keep covered in the fridge for 3 days

nutella swiss meringue buttercream

3 large egg whites
180g caster sugar
230g butter, cut into cubes, at room temperature
180g nutella
pinch salt
seeds scraped from 1 vanilla bean

• combine the egg whites and sugar in the bowl of a stand mixer, place over a pan of simmering water, don't let the bowl touch the water; whisk constantly until the temperature reaches 72ºC 
• return the bowl to the stand mixer and whisk on medium high until the mixture cools, has doubled in size and forms stiff peaks
• change to the paddle attachment and add the butter a piece at a time, mix to incorporate each piece before adding the next; the mixture may look alarmingly curdled at times but keep mixing and it will magically come back together
• once all the butter is in, add the salt and vanilla seeds, mixing on slow until combined, finally add the nutella, again mixing slowly to combine
• the frosting should be firm enough to scoop, if it's too soft, put it in the fridge to firm up, checking in 5 minute intervals until it is ready
• buttercream will keep for a week in an air tight container in the fridge, allow to soften at room temperature before use

nutella ganache

100g nutella
60g chocolate, 70% cocoa solids
125ml cream

• finely chop the chocolate, tip into a small heatproof bowl with the nutella
• heat cream in a small pan until barely simmering, simmer for 1 minute then pour over the chocolate and nutella, stir to ensure the chocolate and nutella are covered by the cream, then let stand for 5 minutes
• stir until smooth and glossy, leave to thicken as it cools