In a small sauce pan, bring blackcurrants (stems removed) and sugar to a boil. Reduce the heat and simmer until the sugar has dissolved completely. Let the mixture cool down completely.
In a large bowl whip heavy cream until stiff. Add Greek yogurt and mix well. Stir in the cooled blackcurrant mixture.
Pour this into a freezer friendly container and throw in fresh blackcurrants. Stir them lightly in.
Freeze for at least 4 hours before serving.
Notes
The time stated above does not include the 20 minutes inactive time needed for cooling the blackcurrant mixture.