Separate the eggs. Beat the egg whites until thick peaks form. In a separate bowl, beat the egg yolks together with the sugar until creamy and then stir in the mascarpone. Break the chocolate and biscuits into small pieces. Fold the egg whites into the egg yolk and mascarpone mixture, stir in the chocolate and biscuit pieces, and finally add the de-seeded grapes. Pour the ice cream mixture into a mold and freeze for around 2 hours until solid. Serve cut into slices.