Soak 2½ sheets of gelatin in cold water for 5 minutes.
Split 1 vanilla bean and scrape out its seeds. Heat the seeds with 150ml of milk, 400ml of heavy cream, and 60g of sugar, stirring, until simmering. Remove from the heat.
Squeeze the water from the gelatin. Stir it into the hot cream until completely dissolved.
Divide between small heatproof dessert glasses. Cool, then refrigerate for at least 4 hours, until set.
