In a saucepan heat 50 gr of caster sugar with 5 tbsp of water en add, once the sugar is melted, the cranberries. Simmer on low for about 3 minutes.
Cut the vanilla bean open length wise. Heat the cream in a saucepan and add the vanilla bean and the 100 g of sugar. Leave to simmer but not really boil for 5 minutes en make sure all sugar is dissolved. Remove the vanilla bean from the cream and scrape the marrow from the vanilla with a sharp knife and add the marrow to the cream.
Soak the gelatine leaves for about 5 minutes in cold water. Squeeze them and add to the hot cream. Stir until dissolved. Leave to cool a bit and then add the buttermilk and the yogurt. Divide the mixture over the panna cotta molds and spoon 1 teaspoon of the cranberries into each form.
Put into the fridge for at least 3-4 hours. To remove the panna cotta from the molds, shortly keep them under a hot tab and put them on plates. Serve with the rest of the cranberries.