Begin by making the custard base. Split the vanilla pod using a small, sharp knife. Scrape out the vanilla seeds. Add the seeds and pod to the milk and cream. Bring the milk, cream and vanilla pod to the boil. Remove from the heat and leave to infuse for at least 10 minutes. Whisk the egg yolks and sugar until pale and fluffy. Reheat the cream mixture until nearly boiling. Strain and whisk into the egg mixture until completely mixed in.
Pour the custard back into the pan and cook on the lowest heat, stirring slowly and continuously for about 10 minutes until thickened. Make sure the spoon touches the bottom of the pan. When done, the custard should be thick enough to coat the back of a spoon. Strain the custard into a bowl and allow to cool, then churn until scoopable. Transfer to a container to freeze before serving.