Make the granita. Place the sugar, measured water and lime rind in a saucepan, heat gently to dissolve the sugar and then bring to the boil. Simmer for 5 minutes, remove from the heat and stir in the mint. Leave to cool and then strain.
Stir the lime juice and vodka into the sugar syrup and transfer to a bowl. Place in the freezer for about 4 hours until frozen.
Remove the ice from the freezer for 15 minutes to soften then transfer to a food processor and blend for 30 seconds until soft and pale. Freeze again if necessary.
Top and tail the pineapple and place it on one end on a chopping board. Using a sharp knife, cut downwards to remove the skin, working all around the pineapple. Quarter and core the pineapple, then cut the flesh into wedges. Spike on to 6 metal skewers, dip in the sugar and barbecue over a medium heat for 2–3 minutes on each side until golden. Cool slightly and serve with the granita.