Happy birthday Luca, with love from Auntie D x

The glorious day has dawned. My lovely godson Luca - thinker, bicycle speed merchant, keen gardener and chocolate connoisseur - is no longer ‘Nearly five!’, he’s really five. Every year, I make his birthday cake, a tradition I plan to continue long after baked offerings from his Auntie D will embarrass his cool, adult self.
I’ve just got back from France, so no time this year for elaborate confections of imaginative shape and refined decoration. Instead, I majored on chocolate, one of Luca’s favourite things in the world, along with frogs, cars and water pipes.
I looked for inspiration to Annie Bell’s fab Gorgeous Cakes and adapted her Chocolate Sensation recipe for the occasion, with the creamy filling for her Birthday Angel Smartie Cake in place of the richer filling she advocates for the rather refined and adult original. Also, I love the combination of raspberries and chocolate. I hope Luca and his friends at the Pirate House will too, or I’ll be walking the gangplank by dusk…
Luca’s birthday cake
There are lots of things I love about Annie’s simple-to-make but impressive-to-eat cake. The buttermilk, vinegar and bicarb combination makes it wonderfully light for a start. Also, the easy, pourable icing takes minutes to make and looks wonderfully glossy on the cake. In her grown-up version, she dips amaretti biscuits into melted chocolate for decoration – a delicious and sophisticated final flourish.

For the cake: 180g unsalted butter, softened
450g caster sugar
3 eggs
400g plain flour, sifted
340ml buttermilk
1 ½ tsp sea salt
1 ½ tsp vanilla extract
75g cocoa powder, sifted
1 ½ tbsps raspberry vinegar or white wine vinegar
1 ½ tsp bicarbonate of soda

For the filling: 300g mascarpone
130g raspberry jam (I like St Dalfour jams – 100% fruit sweetened only with concentrated grape juice. They’re intensely fruity and taste like the best homemade.)
For the icing: 350g chocolate, for Luca’s cake I used 64%, but for an adult version I’d probably go for something of 70% or more
70g unsalted butter
2 tbsps espresso, or strong black coffee (optional)
For decoration: Smarties, of course
Preheat the oven to 180C/350F/Gas mark 4. Butter three 22cm/9in cake tins with removable bases and line the bases with circles of baking parchment. Butter the paper.
Cream the butter and sugar together in a mixer until very light and fluffy – about 6 minutes. Add the eggs, one at a time, beating well between each addition and scraping down the bowl after each egg. Stir in the flour in three stages, alternating with the buttermilk and ending with the last batch of flour (flour/buttermilk/flour/buttermilk/flour). Add the salt, vanilla extract and cocoa. In a small bowl, mix together the vinegar and bicarb – it will fizz quite a bit - then add this to the batter too. Divide the mixture equally between the three tins, smooth gently with a spatula and bake for 20-25 minutes until the cakes shrink from the sides slightly and a cake tester or toothpick inserted into the middle come out clean. Leave to cool for 10 minutes then turn the cakes out onto a wire rack, remove the paper and cool completely.

While the cakes are cooling, make the filling by beating together the mascarpone and raspberry jam until smooth. Chill slightly. When the cakes are completely cool, sandwich them together with the creamy mixture.
To make the icing, melt together half of the chocolate and butter in a small pan over a low heat, stirring until smooth, the stir in a tablespoon of the coffee if you’re using it. Put the cake on a rack and pour over the icing, smoothing it over the sides with a palette knife as you go. Leave it to set for an hour and then repeat with the remaining half of the ingredients, this time pouring over the icing and smoothing it onto the cake as lightly as possible with the palette knife to ensure a nice, glossy coating. Arrange the Smarties over the top and leave for another hour to set. Transfer to a cake plate or board. If you like, you can store the cake in an airtight container in the fridge for a couple of days, but bring it back up to room temperature for half an hour before serving.