For the panna cotta, put the gelatine leaves in a small bowl of cold water to soften – this will take about 5 mins. Meanwhile, pour the cream, milk and sugar into a pan, split the vanilla pod, scrape out the seeds and add, along with the pod, to the cream mixture. Heat gently until hot, but not bubbling. Remove the gelatine leaves from the water, squeeze out any excess liquid then add, one at a time, to the hot cream. Stir until dissolved. Leave to stand for 20-30 mins until cooled – the vanilla pods should be suspended in the liquid by this point. Strain the mixture through a sieve into 6 serving glasses, then chill for at least 3 hrs.