Prepare berries: Rinse the berries under cold running water, drain well in a sieve. Remove the stems. Weigh the needed berries after you've removed the stems.
Cook: Place in a small saucepan. Add lemon juice and cordial. Bring to a gentle boil and simmer until the berries pop and the mixture thickens slightly, about 3-4 minutes. Set aside and let cool completely. When cool, blend with a hand-held blender or in a blender. Set aside.
Mix: Beat the cream until soft peaks form. Set aside. Mix the sweetened condensed milk with the black currant puree. Carefully fold in the whipped cream.
Freeze: Line the bottom and the walls of a small loaf tin with cling film/plastic wrap. Pour the mixture into the container. Cover with another piece of plastic wrap directly over the surface. Freeze for at least 8 hours or until solid.
Serve: Remove from the freezer for about 10 minutes before scooping to allow it to soften slightly. Serve in ice cream cones or small bowls.