Step 1

Begin by preparing the white chocolate mousse. Add the white chocolate to a heatproof bowl and melt in the microwave on a low setting. Alternatively, place the heatproof bowl over a pan of gently simmering water and stir until melted

Step 2

Soften the gelatine in cold water for 4-5 minutes. Meanwhile, add 120g of the double cream and 10g of the milk to a pan, bring to a simmer, then remove from the heat. Squeeze any excess moisture out of the softened gelatine and add to the cream, stirring until the gelatine has dissolved

Step 3

Add the remaining cream and milk to a bowl and whisk until very soft peaks form. Whisk the warm cream into the melted chocolate to make a ganache, then allow to cool to between 35-40°C. Once it has reached this temperature, fold in the whipped cream. Transfer to a container and allow to set in the fridge for at least 2 hours

Step 4

For the lemon curd, zest the lemons directly into a heatproof bowl to help retain all of the essential oils from the zest - the bowl will need to be the correct size to sit over a pan to make a bain marie

Step 5

Firmly roll the zested lemons on a work surface to help them soften and increase the yield when juicing, then squeeze the juices into the bowl with the zest

Step 6

Add the sugar and butter, then place the bowl over a pan of gently simmering water. Allow the mixture to melt together, stirring occasionally to combine

Step 7

Once the mix is fully dissolved and fairly warm, whisk in the eggs and egg yolk. Cook the mixture, stirring frequently until thickened - the curd needs to be kept at 79°C for a minimum of 15 seconds to pasteurise the eggs

Step 8

Pass the curd through a fine sieve and pour into sterilised jars. Seal and allow to cool in the fridge until required. The curd can be kept in the fridge for 4-8 weeks

Step 9

For the sponge, add the duck egg yolks to a bowl and whisk in two thirds of the sugar until thick and pale. Add the whites to a separate bowl and whisk until soft peaks form, then whisk in the remaining sugar. Keep whisking the egg whites until you have a thick and glossy meringue

Step 10

Preheat the oven to 160°C/gas mark 3

Step 11

Add one third of the meringue into the egg yolk mix and stir to combine. Gently fold in the remaining meringue and once almost combined, gently fold in the sifted flour. Finally, fold through the lemon zest

Step 12

Line a Swiss roll tin with silicone paper and grease lightly with butter. Dust with a little flour, then tip the sponge mix into the tin, levelling out with a palette knife to ensure an even finish. Place in the oven for 8-10 minutes until risen, firm to the touch and golden

Step 13

Remove the sponge from the oven and sprinkle with caster sugar. Quickly turn out onto a sheet of silicone paper and remove the (now top) layer of paper. Use a sharp pastry knife to neaten the edges and roll up the sponge to form a roulade. Leave the roulade to cool

Step 14

Once ready to assemble, carefully unroll the sponge, taking care not to break it. Weigh out 150g of the lemon curd and use a palette knife to spread the curd in an even layer over the sponge, ensuring to leave a 2cm border around the edges

Step 15

Arrange three quarters of the mousse into the centre of the sponge (on top of the lemon curd layer) and work it towards the outer edges, again leaving a 2cm border. Roll up the sponge, enclosing the filling and finishing with the seam at the bottom of the roll

Step 16

Spread a thin layer of the remaining white chocolate mousse over the outer surface of the roulade. Use a knife to shave thick curls of white chocolate, keeping the knife towards you at an angle of approximately 30

Step 17

Top the roulade with the chocolate curls, then finely grate the green pistachios on top. Place in the fridge to set, removing 1 hour before serving