Inspired by the Austrian speciality sachertorte, this cake is a chocaholic’s dream. White, milk and dark chocolate gluten-free sponge layers are sandwiched with slightly tart apricot jam. Shades of white, milk and dark chocolate buttercream create stripes around the outside of the cake that mirror the layers inside.
Heat the oven to 180°C/160°C fan/350°F/Gas 4.
First, make the apricot jam. Put the apricots and caster sugar in a medium saucepan and place over a low heat. Let the sugar melt, then slowly bring the liquid to the boil. Increase the heat and boil for a further 10–15 minutes, until the temperature on the sugar thermometer reaches 105°C (alternatively, test a teaspoon of jam on a saucer that has been kept in the freezer for 20 minutes –if it wrinkles when you press it, the jam is ready). Remove from the heat. Leave to cool and set.
Make the sponges. First, make the white chocolate sponge. Whisk the eggs, sugar, vanilla and salt in a stand mixer fitted with the whisk attachment, on medium speed, for 3–5 minutes, until pale and thick.
Meanwhile, put the white chocolate, milk and butter in a small saucepan set over a medium heat, stirring to melt the chocolate and butter. When everything is combined, remove the pan from the heat and set chocolate mixture aside to cool to room temperature.
Pour the egg mixture into a large mixing bowl and sift in the flour, baking powder and xanthan gum. Gently fold the dry ingredients through the wet, until fully combined.
Fold the cooled chocolate mixture into the batter, until fully incorporated. Pour the batter into one of the prepared cake tins and set aside.
Repeat steps 3–6 for the milk and dark chocolate sponges, re-using the bowls and saucepan as necessary.
Once you have prepared the batters for all three layers, bake the sponges for 30–35 minutes, until they are risen and firm to the touch and a skewer inserted into the centre of each sponge comes out clean. Remove the sponges from the oven and leave them to cool in the tins.
Make the apricot syrup. Heat the sugar and 3 tablespoons of water in a heavy-based saucepan over a low heat, gently swirling the pan from time to time (but don’t stir), until the sugar dissolves. Remove from the heat and stir in the apricot brandy. Set aside.
Make the buttercream. Heat the sugar with 6 tablespoons of water in a heavy-based saucepan over a low heat, gently swirling the pan from time to time (but don’t stir), until the sugar dissolves.
Increase the heat, bring the syrup to the boil and continue to cook until the temperature on the sugar thermometer reads 115°C. At this point, whisk the eggs, egg whites and vanilla extract in a stand mixer fitted with the whisk attachment on high speed for 3–5 minutes, until pale and thick.
Once the sugar thermometer reads between 118°C and 121°C, with the mixer running, slowly pour the syrup into the eggs. Continue whisking until the bowl of the stand mixer is cool to the touch.
Meanwhile, melt each chocolate in its own heatproof bowl in 30 second bursts in the microwave. Set aside to cool to room temperature.
Switch the stand mixer to the beater attachment. Gradually, add the softened butter to the cooled meringue mixture, beating continuously until smooth.
Put one third of the buttercream into each bowl of melted chocolate and beat with a spatula to fully incorporate. Spoon each chocolate buttercream into a piping bag fitted with a large round nozzle.
Pipe dots of the dark chocolate buttercream onto the cake board. Place the dark chocolate sponge on the board and brush it with some of the apricot syrup. Pipe a thin layer of the dark chocolate buttercream over the sponge and spread half of the apricotjam over the buttercream, leaving a border of about 1cm around the edge. Place the milk chocolate sponge on top and repeat with the milk chocolate buttercream and remaining apricot jam. Top with the white chocolate sponge. Spread the top and sides of the cake with a thin, even layer of the white chocolate buttercream to create a crumb coat, then chill the stacked sponges for 30 minutes to firm up.
Meanwhile, prepare the chocolate drip. Tip the chocolate into a heatproof bowl. Pour the cream into a small saucepan and bring it just to the boil over a medium heat. Pour the hot cream over the chocolate in the bowl and leave it for 2 minutes, then stir until smooth. Transfer the drip either into either the squeezy bottle or the small piping bag. Set aside.
Remove the cake from the fridge and place it on a cake-decorating turntable if you have one (this makes decorating easier, but it’s not essential). Pipe a ring of dark chocolate buttercream around the base of the cake, top with further rings as necessary until you are one third of the way up the side of the cake. Next, pipe rings of milk chocolate buttercream, working your way up another third of the cake, then finally use the white chocolate buttercream to pipe rings up the final third and across the top of the cake. The side and top of the cake should now be completely covered in buttercream.
Using a palette knife gently smooth out the buttercream into neat stripes around the side and smooth out the top. Using a smooth cake scraper, smooth the buttercream stripes to give a neat finish.
Pipe blobs of chocolate ganache (snip the end of the piping bag if that’s what you’re using) around the top edge of the cake, allowing it to drip down the side. Pipe alternate blobs of the remaining buttercreams all over the top of the cake to finish.