Cook blackcurrants, sugar, and water in a pan for ten minutes until berries break down.
Strain the mixture through a sieve into a clean pan to form 300ml of purée.
Stir the crème de cassis into the juice and set aside.
Soften gelatine sheets in cold water for five minutes.
Heat cream and milk until almost simmering, then dissolve the squeezed gelatine into the mixture.
Combine the cream mixture with the blackcurrant mixture until smooth.
Pour mixture into a 1 litre mould and chill for 8 hours until set.
Dip the mould into hot water for five seconds to release the cream onto a plate.
Slice and serve with extra blackcurrants and cream.