In a saucepan over medium heat, combine milk and vanilla bean and bring mixture just to a simmer and remove pan from heat. Do not let it boil. Pull out vanilla bean and using the back of a small knife, scrape any remaining seeds into the milk.
In a large bowl, whisk together egg, egg yolks, sugar and salt until mixture lightens in color, about 1 minute.
Slowly whisk the hot milk mixture into the egg mixture, whisking constantly until well blended. Pour mixture back into saucepan.
Over low heat, whisk mixture constantly until it thickens and coats the back of a spoon. Do not let it bubble or the eggs will start to scramble.
Transfer to a blender, add the vanilla extract and blend until smooth.
Crème Anglaise can be made in advance and stored in an airtight container in the fridge for several days.