This is a stunning show-off dessert – cut through the shiny mirror glaze to reveal layers of honey-and-lemon mousse and raspberry curd, and a sponge all covered with white chocolate bavarois. The cake is a little time-consuming to make, but totally worth the effort.
Make the lemon and honey mousse. Soak the gelatine leaves in a bowl with 4 tablespoons of water. Meanwhile, place the honey, lemon zest and juice and vanilla paste in a medium pan over a medium heat. Cook for 2–3 minutes, until the mixture darkens a little and thickens to a syrup. Remove from the heat, then whisk in the double cream and milk until combined. Return to the heat and bring to just below boiling point.
Place the egg yolks, salt and sugar in a small bowl and whisk together with a balloon whisk, then pour the hot honey-cream mixture over. Whisk to combine, then return the mixture to the pan. Stir continuously over a low heat for about 5 minutes, until the custard thickens. Remove from the heat.
Remove the gelatine from the water, shake off the excess and add it to the custard mixture. Stir until dissolved, then strain the custard and pour it into one of the 15cm tins lined with cling film. Place in the freezer to set for no more than 45 minutes, then transfer to the fridge until you’re ready to assemble.
Make the raspberry curd. Soak the gelatine leaves in a bowl with 4 tablespoons of water. Meanwhile, purée 250g of the raspberries in a blender, then sieve the purée to get 100g of juice. Place the juice in a pan over a medium heat and bring almost to the boil.
Place the eggs and sugar in a small bowl and, using a balloon whisk, whisk for 2–3 minutes, until combined. Gradually whisk in the hot raspberry juice, then return the mixture to the pan, add the butter and heat over a low heat, stirring continuously with a wooden spoon, until thick enough to coat the back of the spoon. Remove from the heat.
Remove the gelatine from the water, shake off the excess and add to the raspberry mixture. Stir until dissolved, then stir in a little red food colouring, if desired. Pour the mixture into the remaining 15cm tin lined with cling film. Place the remaining whole raspberries in the curd, and transfer to the freezer to set for no more than 45 minutes. Transfer to the fridge until you’re ready to assemble.
Make the lemon génoise. Heat the oven to 180°C/160°C fan/350°F/Gas 4. Place the eggs, lemon zest and sugar in the bowl of a stand mixer fitted with the whisk. Whisk on high speed for 2–3 minutes, or until the mixture leaves a ribbon trail when you lift the whisk.
Using a large metal spoon, fold in the flour, then the cooled melted butter and the lemon juice. Spread into the 20cm springform tin and bake for 12–15 minutes, or until golden and just firm to the touch. Leave to cool in the tin for 5 minutes, then turn out onto a wire rack to cool completely. When cold, using a sharp, serrated knife, cut the sponge in half horizontally. Wash and dry the tin and line the sides with the strip of acetate.
Place one round of sponge in the tin. Place the honey-flavoured custard onto the centre of the sponge, removing the tin and cling film, then top with the raspberry curd, again removing the tin and cling film. Return the assembly to the fridge. (You can eat the remaining round of sponge, or break it up, freeze it and use it for trifle another time.)
For the white chocolate bavarois, soak the gelatine leaves in 6 tablespoons of water. Meanwhile, place the egg yolks and sugar in a small bowl and, using a balloon whisk, whisk until combined. Pour the milk into a small pan and heat until just below boiling point, then gradually whisk this into the egg and sugar mixture.
Pour the mixture back into the pan and cook over a low heat, stirring continuously with a wooden spoon, until it thickens and coats the back of the spoon. Remove the gelatine leaves from the water, shake off the excess and add to the pan. Then, add the white chocolate and stir until the gelatine has dissolved and the chocolate has melted. Pour the mixture into a bowl and leave to cool for 15 minutes.
Using a hand-held electric whisk, whisk the cream until it forms soft peaks and fold this into the cooled chocolate mixture. Leave for 15 minutes, until just beginning to set, then pour it around the honey and raspberry layers on top of the sponge. Leave to set in the fridge for at least 4 hours.
Make the mirror glaze. Soak the gelatine leaves in 8 tablespoons of water. Meanwhile, place 75ml of water in a small pan with the sugar and glucose and place over a medium heat. Heat until the mixture reaches 103°C/217°F on the sugar thermometer, then remove from the heat.
Remove the gelatine leaves from the water, shaking off the excess, and add them to the syrup in the pan along with the condensed milk and chocolate. Stir until the chocolate has melted. Pour into a bowl and add blue food colouring to create the desired shade. Leave to cool to about 30°C/86°F.
Using the kitchen blow torch, very gently warm the outside of the springform tin. Undo the clip and remove the ring. Slide the cake onto the thin cake board and place on a wire rack set over a tray (to catch the drips). Pour most of the glaze evenly over the cake. Add some more food colouring to the remaining glaze in the bowl, then pour that over the top of the glaze layer. Swirl the mixture together to create an ocean effect.
To make the decorations, one by one, melt each colour of isomalt in a heatproof jug in a microwave following the packet instructions (it will usually take 3–4 minutes at a medium microwave temperature). Pour it into the bowl containing the crushed ice and allow it to set for 3–5 minutes, until solid. Carefully peel away the decoration and position it on top of the cake. Repeat for the remaining colours. Place the cake in the fridge to set for at least 20 minutes before serving.