Start this recipe by soaking the gelatine leaves in cold water to soften them. Meanwhile, prepare the panna cotta. Place the cream, buttermilk, caster sugar and vanilla pod or essence in a saucepan and heat to almost boiling point. Add the soaked gelatine leaves (remove the water) and whisk till the gelatin has completely dissolved. Pass the liquid through a sieve to remove any lumps, and then carefully pour into your moulds using a ladle or jug. Place the filled moulds in the fridge for at least 2 hours to set, or overnight. To make the coulis, press ½ of the berries through a sieve to extract the juices. Discard the mush that is left in the sieve, and add the icing sugar to the berry juices to sweeten the coulis. When the panna cotta is set and you are ready to serve them, place the moulds in hot water for 2 seconds to release the panna cotta from the sides of the mould. Tip out onto your serving plates, and decorate each serving plate with a tablespoon of the berry coulis. Finally, decorate the buttermilk panna cotta with some fresh berries and mint leaves on the side.