Halve the limes and squeeze the juice. Cut avocados in half, remove stones and peel the flesh. Mix the pulp with lime juice, vanilla sugar, coconut syrup and coconut liqueur and puree in a blender. Pour the avocado puree into a metal bowl and place in the freezer for at least 5 hours. Stir several times. Leave to stand at room temperature for about 10 minutes before serving. Arrange in tall glasses and decorate with raspberries and coconut spirals as desired