Black Forest gâteau gets a total makeover with this impressive, layered cake. You’ll need patience because it will put your baking skills to the test, but the stunning effects of the finished bake will make every bit of effort worthwhile.
Use the pattern template to draw a hexagonal geometric pattern on the 33 x 23cm sheet of baking paper. Turn the paper over, so that the pencil is on the underside, and use the paper line the greased Swiss roll tin.
Make the decorative paste. Beat the butter and icing sugar in a stand mixer fitted with the beater, on medium speed for about 3 minutes, until pale and creamy, scraping down the sides of the bowl from time to time.
Add the egg whites, a little at a time, beating well between each addition. Add the vanilla and beat again, then add the flour and beat on a low speed until fully incorporated.
Spoon 2 tablespoons of the mixture into a small bowl and colour this red. Spoon this into the small piping bag. Transfer the remaining mixture into the large piping bag and snip the end of each bag to make a small hole.
Using the white icing, pipe the outline of the geometric pattern on the prepared baking paper. Use the red mixture to fill the centre of some of the hexagons at random. Place the paper, on the baking sheet, in the freezer for the icing to set while you prepare the joconde.
Using a cake tin or plate as a guide, draw two 18cm-diameter circles on the baking paper lining the baking sheet, leaving space between each one. Set aside.
Make the chocolate joconde. Mix the cocoa powder with the melted butter to a smooth paste, then set aside.
Beat the eggs with the ground almonds, icing sugar and flour in a stand mixer fitted with the beater, on medium speed for 3–5 minutes, until creamy. Add the cocoa and butter mixture and beat again to combine. Transfer the mixture to a separate bowl and set aside.
In a clean bowl, whisk the egg whites in a stand mixer fitted with the whisk, on medium speed for 3–5 minutes, until they form soft peaks.
Gradually add the caster sugar, 1 tablespoon at a time, whisking continuously. Once you have added all the sugar, increase the speed to maximum and whisk for about 5 minutes, until you have a stiff and glossy meringue.
Add one third of the meringue to the ground almond mixture and thoroughly stir it in to soften and lighten the texture. One third at a time and using a large metal spoon or plastic spatula, fold in the remaining meringue.
Heat the oven to 180°C/160°C fan/350°F/Gas 4.
Spoon half the mixture into the Swiss roll tin, being careful to not dislodge the pattern. Spread the mixture out evenly, using an offset spatula, making sure you completely fill to the corners.
Spread the remaining mixture inside the circles that you have drawn on the baking paper, to create discs.
Bake all of the sponges for 10–12 minutes, until firm to the touch and leave them to cool for 10–15 minutes. Place a new sheet of baking paper over each sponge and then turn out the sponges on to wire racks. Peel off the uppermost sheets of baking paper on each sponge and leave the sponges to cool completely.
Meanwhile, prepare the cherry juice. Place the cherries, sugar and a squeeze of lemon juice in a saucepan set over a low heat. Heat gently until the sugar has dissolved, then remove the pan from the heat. Using a hand-held stick blender, blitz the cherry purée. Strain it through a sieve into a bowl and set aside.
Take the cooled rectangular joconde sponge and cut 2 long strips to fit tightly inside around the wall of the 20cm springform tin (against the acetate lining) and so that they sit 1cm above the rim. Press together the ends of the strips to make sure there are no gaps where they join.
Using the 18cm cake tin or a plate as a guide again, trim the 2 discs of chocolate joconde sponge to neaten the edges and place one into the tin, to line the base. Keep the other sponge disc to one side.
For the cherry mousse, place the gelatine leaves in a bowl of water and leave them for 5 minutes to soften. Place the cherries and caster sugar in a saucepan set over a medium heat, bring to the boil and reduce by one quarter. Drain the gelatine, squeezing out the excess water, and whisk the leaves into the cherry purée in the pan until completely dissolved. Using a hand-held stick blender, blitz the mixture until smooth, then pass it through a sieve into a bowl. Leave to cool. Meanwhile, in a separate bowl, whisk the double cream to soft peaks, then add it to the cooled cherry mixture in and whisk it to combine.
Generously brush the sponge lining the base of the tin with half the cherry juice. Spoon the cherry mousse on top of the sponge and spread it out evenly. Place the second sponge disc on top of the cherry mousse and brush it with the remaining cherry juice. Chill while you make the bavarois.
Make the chocolate bavarois. Place the gelatine leaves in a bowl of water and leave them for 5 minutes to soften. Meanwhile, heat the milk in a saucepan to just below boiling point. At the same time, melt the chocolate in a heatproof bowl set over a pan of barely simmering water. Stir the chocolate until smooth. Remove both the milk and the chocolate from the heat.
While the chocolate is melting, whisk the egg yolks and caster sugar together until pale and creamy. Pour the hot milk over the eggs, whisking them together as you pour, to form a custard. Return the custard to the pan and cook it until the mixture has thickened enough to coat the back of a spoon. Remove the custard from the heat and pour it over the melted chocolate. Stir to combine.
Drain the gelatine, squeezing out any excess, and whisk it into the chocolate custard until it dissolves. Leave it to cool to room temperature.
Using a hand-held electric whisk, in a large bowl, whisk the cream to soft peaks. Half at a time, fold in the cooled chocolate custard. Spoon the mixture onto the sponge in the tin and spread it out evenly. Return the sponge to the fridge until the bavarois has set firm.
To make the chocolate decorations, melt 75g of the chocolate in a heatproof bowl set over a pan of barely simmering water until the chocolate reaches 41°C on a cooking thermometer. Remove the bowl from the pan, and stir in the remaining 25g of chocolate. Stir until the added chocolate has melted and it has all cooled to 32°C. (This is known as tempering.)
Place the acetate strip on a sheet of baking paper and, using a small spoon, thickly splatter the tempered chocolate on the acetate. Carefully, curl the acetate and slide it inside the two 4cm cutters, using them to hold the acetate in place. Chill until set and then carefully peel off the acetate and spray the chocolate with gold dust, if you wish.
When you’re ready to serve, remove the cake from the fridge. Trim the sponge neatly around the edge so that it is level with the top of the chocolate bavarois and dust the top with cocoa powder. Unclip the tin, peel off the acetate and place the cake on a serving plate. Decorate with the cherries and chocolate curl.