Cut the top off the pineapple complete with its leaves. Put it into the refrigerator to chill. Hollow out the pineapple with a small knife, taking care not to pierce the outside shell which should be 1cm (½inch) thick. Put the shell in the ice-making compartment of the refrigerator.
Cut away the hard central core of the pineapple, and cut the remaining flesh into small pieces. Purée it in a liquidiser or through the fine blade of the mouli-légumes. Add 100g (3½oz) of caster sugar or icing sugar and beat it in with a wire whisk.
Transfer the mixture to the ice-cream maker and freeze it. Then using a spoon dipped into hot water, pack the mixture into the chilled shell of the pineapple. Put the tuft of leaves back on top, and serve.