Put aside two or three handsome bunches of currants (with leaves on, if there are any).
Remove the stalks from the rest of the currants and purée them in a liquidiser or with the finest blade of the mouli-légumes. Pass through a fine sieve, add the sugar, and beat it in well with a whisk. Transfer the mixture to the ice-cream maker and freeze. When you serve the sorbet scoop it out in balls with a spoon dipped into hot water.
Take the bunches of currants which you have kept aside and dip them first into iced water and then into caster sugar so that they are prettily frosted. Arrange them on top of the sorbets.