Pour double cream and whole milk into a pan with the seeds and casing of a vanilla pod. Heat the mixture until it boils, then immediately take it off the heat.
In a food processor, beat organic free-range egg yolks and raw organic caster sugar to a thick, pale yellow consistency.
From the boiled cream mixture, carefully remove the vanilla pod, then thinly dribble the hot milk liquid into the egg mix, keeping the food processor going all the time to prevent the mixture from curdling. Then return the combined eggs yolks, sugar and milk back to the saucepan and heat gently, stirring constantly, until the mixture begins to thicken. Remove from the heat and allow the mixture to cool down to room temperature.
In a blender, reduce your blackberries to a pulp and sieve to remove any lingering pips. Stir the gorgeously bright purple smooth berry purée into the custard mixture.
Churn the combined mixture in an ice cream maker until it’s frozen. Spoon into a freezer-proof container and freeze for at least an hour.