Halve the vanilla pod, scrape out the pulp and bring both to the boil with the milk. Whisk the egg yolks, sugar, cream and some milk together and pour into the simmering vanilla milk while stirring and bring to the boil briefly. Pass through a sieve and pull in the stiffly beaten egg white.
Arrange the apples on plates with the vanilla sauce as a mirror and pour the burning calvados over them.