Line six 125ml/4fl oz pudding moulds with clingfilm. To make the whisky cordial, place the whisky, white currants, sugar, lemon zest and ginger in a saucepan and heat gently. Do not allow the mixture to boil. Strain and push the pulp through a fine sieve to extract the juice then set aside to cool.
For the semifreddo, place the egg yolks and sugar in a bowl set over a pan of barely simmering water and whisk until the mixture is pale and thick. Remove the pan from the heat and continue to whisk until the mixture is cool.
Mix 125ml/4fl oz of the whisky cordial into the semifreddo mixture a tablespoon at a time. Whisk the cream until it forms thick ribbons then fold it into the semifreddo. Pour the mixture into the lined moulds and freeze overnight.
For the garnish, prick the whitecurrants with a pin and place in a bowl with the remaining whisky cordial. Place in the fridge to macerate overnight.
To serve, turn the semifreddos onto plates and scatter with the macerated white currants.