Raspberry ripple and pistachio parfait

Method

1. To make the raspberry sauce, put the 100g sugar in a heavy-based saucepan with a splash of water and heat very gently until the sugar has dissolved. Bring the mixture up to the boil and bubble for 5-10 minutes until reduced and syrupy. Stir in the raspberries, then cook for a few minutes more until the berries have almost completely broken down. Remove the pan from the heat, then push the raspberry syrup through a sieve into a mixing bowl (discard the seeds). Set aside to cool completely with a sheet of cling film touching the surface.
2. Line a 450g loaf tin with a double layer of cling film, leaving a bit of overhang. Put the egg yolks, 50g caster sugar and vanilla bean paste in a large bowl, then whisk with an electric mixer or a balloon whisk until thick and pale. Whip the cream to soft peaks, then fold gently into the egg yolk mixture using a balloon whisk. Whisk the egg whites in another bowl with clean beaters or a clean balloon whisk until very stiff, then gently fold them through the creamy yolk mixture with the whisk.
3. Gently fold through the pistachios, then spoon a third of the mixture into the prepared tin and dollop some of the cold raspberry sauce on top. Repeat twice more, then cover lightly with the overhanging cling film and freeze for around 8 hours or up to 2 weeks (see Make Ahead).
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5. When ready to serve, remove the parfait from the freezer and leave to soften for a few minutes. Unwrap the cling film on top and use it to lift the parfait from the tin. Invert onto a serving platter, then peel off the cling film. Dip a palette knife in a mug of just-boiled water to warm, wipe dry, then use the flat of the knife to smooth away the marks from the cling film (or use a chef’s blow torch if you have one). Leave for 10 minutes to soften, then slice. Serve scattered with fresh raspberries, honeycomb, extra pistachios and any leftover sauce.