Put the egg yolks, sugar and wine in a heatproof bowl over a pan of simmering water, making sure the base of the bowl isn’t sitting in the water. Gently whisk until pale and foamy. Remove from the heat and chill in the fridge.
In a separate bowl, whisk the cream until stiff. When the egg mixture is chilled, add the whipped cream, yoghurt and sorrel juice. Pour into a shallow tray lined