Whisk the egg yolks with the sugar and salt until pale. Cut the vanilla pods in half lengthwise and scrape out the seeds. Bring the milk and cream to the boil with the vanilla, and then slowly pour it into the egg while whisking.
In a clean pan, heat the custard while stirring continuously until it thickens. Avoid heating it to more than 86°C. Pass through a chinoise into a clean bowl s