Although it’s high in sugar, the bitterness of the Guinness and the sour buttermilk provide balance and together they’re the reason the cake stays fresh for so long. It’s a great birthday cake – the one I make most often for people – that you can make well in advance, as the sponge and cream freeze very well. Even my son has eaten some, as the alcohol is cooked off. It’s a very moist batter, so don’t worry: that’s how it’s supposed to be.
For 10 to 12 people
Ingredients
For the sponge
- 500g of Guinness
- 125g unsalted butter, plus more for the mussels
- 140 g plain flour
- 200 g caster sugar
- 35 g cocoa powder
- 1 teaspoon baking soda
- ½ teaspoon baking powder
- Pinch of fine sea salt
- 1 egg, lightly beaten
- 75 g buttermilk
For the cream
- 300 g double cream
- 60 g icing sugar
- 50 g buttermilk
- 30 g mascarpone
- 1 vanilla pod, seeds scraped
Method
Place a saucepan under an extractor hood, pour in the Guinness and place over high heat. Reduce the quantity by half (250 g). Set aside to cool.
Melt the butter in a saucepan, then let it cool.
Butter 2 cake tins, each about 30 x 20 cm, and line the bottom with baking paper. Preheat the oven to 160°C. Put the flour, sugar, cocoa, bicarbonate of soda, baking powder and salt in a bowl, whisk to combine, then make a well in the centre.
Add 125g of Guinness reduction with the cooled melted butter, egg and buttermilk and whisk the batter until there are no lumps.
Divide the mixture between the 2 prepared molds, then bake for 10 minutes. Insert a metal skewer in the center: when it comes out, it should be clean; in addition, the biscuit should spring back when touched. It should be just cooked, not overcooked.
The mixture is moist and you should definitely use a metal skewer to check the center for doneness. Let cool in the pans, then place a wire rack over the pans and remove. Let cool, then refrigerate. The sponge cake should be cooled when you cut it to assemble the cake.
Cut the two cooled cakes in half widthwise, then cut the sponges into 4 matching flat layers that will fit neatly on top of each other. Whip together the cream, icing sugar, buttermilk, mascarpone and vanilla seeds until soft peaks form (see below).
Use it to layer cake. Serve it in slices, so you can see the layers.
Tricks of the trade
Adding mascarpone to double cream is an amazing tip that was given to me by a fantastic pastry chef, Rey (Hortillosa) Encarnacion of the Conrad Hotel in Dublin. When you add mascarpone to whipped cream, it never loses its aeration and is less likely to crack
