Place a container with a tight-fitting lid in your freezer. Wash and the blackcurrants and place them in a saucepan. Slowly bring to the boil over medium heat until they start to pop and release their juice.
Push the blackcurrants through a fine sieve to retain the seeds and skins.
Add the sugar while still warm and stir until it dissolved. Taste for sweetness and add more sugar if desired. Stir in the vanilla extract and let cool.
Beat the double cream until stiff. Fold it under the blackcurrant mixture.
Tip into the precooled container and freeze until the ice cream is hard enough to be shaped with an ice cream scoop, about 2 hours.