Oil a 900g loaf tin and line with cling film. Tip the sugar and eggs into a heatproof bowl set over a pan of simmering water, ensuring the bowl doesn’t touch the water, then whisk until pale and doubled in volume. Remove from the heat and plunge the base of the bowl into a second, larger bowl filled with cold water and keep whisking until completely cooled.

Melt the chocolate in a heatproof bowl in 20-second bursts in the microwave, or in a heatproof bowl set over simmering water, as in step 1. Whip the cream to soft peaks in another bowl using an electric whisk and fold the chocolate into it, along with the passion fruit, lemon zest and juice. Using a large metal spoon, add a spoonful of the whipped egg mixture and stir to loosen before folding in the rest.

Tip the pistachios into the prepared tin, spoon over the semifreddo mixture and smooth the surface. Cover with cling film and freeze overnight. Will keep frozen for up to a month. Remove from the freezer 15-20 mins before serving. Dip a sharp knife into boiling water, then slice.