Pour the milk into a pan and add the vanilla seeds and the pod. Heat until almost boiling (you’ll notice it steaming).
Beat together the egg yolks and sugar until pale. Whisk in the flour and cornstarch until combined.
Once the milk starts to boil, pour half into the egg yolk mixture and whisk continuously to combine (tempering). Pour this mix back into the pan with the rest of the milk. On a medium heat, keep whisking until it thickens. This should take around 2 minutes.
Once thickened, boil for 1 minute but make sure to keep whisking. Remove the vanilla pod. Cook for a further minute and whisking constantly.
Pour the pastry cream onto a baking tray and cover tightly with cling film (press the film so it sticks to the cream to push out air bubbles), ensuring there’s as little air bubbles as possible. Leave to cool to room temp.
Before use, remove from the tray and whisk in a bowl to loosen. If not using straight away, remember to refrigerate.
Notes
Storage - Ensure you refrigerate your pastry cream if not using straight away. Store in a sealed container. It'll keep for 3 days in the fridge.Freezing - Pastry cream cannot be frozen as the texture is ruined once thawed. If you chose not to use cornflour and just plain flour, you will be able to freeze your pastry cream. I've not frozen any before (I always use cornflour) so check out DIYS for how-to.