Whisk the egg yolk with the sugar in a bowl until the mixture turns pale.
Add the cornstarch and mix.
Bring the milk to a boil with the seeds from the half vanilla pod and the pod itself.
Pour the hot milk through a strainer over the egg mixture.
Stir everything together and return to the saucepan.
Cook over medium heat, stirring constantly, until it thickens.
Transfer to a dish and cover with plastic wrap, ensuring it touches the surface.
Refrigerate for about an hour. It must be cold before incorporating it into the almond cream.