Put the redcurrants, sugar and orange juice and zest into a large pan with 100ml water. Cook gently for 5-10 minutes until the redcurrants have burst.
Whizz in a food processor or blender then push through a sieve (taste and add a little more sugar if needed). Stir in the wine. Pour into a large baking dish and freeze for at least 4 hours. Serve in small glasses.