Pour the milk in a pot and make it boil with the sliced vanilla pod.
Meanwhile, mix together the eggs, the sugar and the cornflour, to get a creamy batter.
Once the milk has boiled, add it to the mix while whisking.
Put it all back on heat (at medium temperature), and thicken it while stirring for about 15 minutes.
Put your pastry sheet in a baking mold, then pour the custard in it.
Bake for 45 minutes at 360°F (180°C)
There you are, your "flan pâtissier" is ready ! Bon appétit !