Place the cream and milk in a saucepan. Use a sharp knife to split the vanilla beans lengthways, and then scrape the seeds from inside of the beans. Add the seeds and bean to the saucepan. Slowly bring to the boil over a medium heat. Remove from the heat and set aside for 10 minutes.
Remove beans from cream mixture. Add sugar and return to a low heat. Cook stirring for 4 minutes until sugar dissolves.
Sprinkle gelatine into a little hot water Bring a small saucepan of water to boil. Remove from heat. Mix the gelatine in the water and stir until dissolved. Cool slightly, and then stir into the cream mixture.