Preheat your barbecue. Beat the crème fraîche with the seeds from the vanilla pod and put to one side. Cut the ends off the pineapple. Sit it on a board and cut off the skin in wide strips from top to bottom, making sure you cut out any woody eyes. Thinly slice the pineapple, and dust the slices with icing sugar. Make sure the bars of the barbecue are clean – especially if you’ve been cooking fish or meat beforehand – and drop the slices of pineapple on to it. Grill for about 30 seconds on each side then lift off with the tongs and transfer to a serving plate. Serve scattered with mint and a generous dollop of vanilla-flavoured crème fraîche.