Sprinkle the gelatine over the cold water in a small bowl and set aside for 5 minutes. Meanwhile, slit the vanilla pod along its length and scrape out the seeds with a small knife, add to a saucepan with the pod, cream, milk and 50 g (2 oz) of the icing sugar.
Bring the cream mixture to the boil, add the gelatine, take off the heat and stir until the gelatine has completely dissolved. Leave to cool for 20 minutes, stirring from time to time so that a skin doesn't form. Remove the vanilla pod and discard. Divide the vanilla cream between six 150 ml (5 fl oz) individual metal pudding moulds. Allow to cool, then chill for 4–5 hours until set.
Mix the strawberries with the remaining sugar and the Pimms, if using. Cover and chill until required.
When ready to serve, dip the bases of the moulds into hot water for 10 seconds, then loosen the top edge, invert on to a small plate and jerk to release dessert. Lift off the mould and spoon strawberries around the dessert. Serve decorated with mint leaves.