Place the egg yolks and caster sugar in a mixing bowl and whisk until the sugar is dissolved and the mixture is slightly paler in colour.
Add the cornflour and whisk well so there are no lumps of flour left. Place the bowl on a folded, dampened tea towel in readiness for the next stage.
Put the milk in a medium saucepan along with the vanilla and place over a medium-high heat until just before the milk boils. Pour half this milk into the bowl with the eggs, whisking continuously as you do so; the dampened tea towel helps stop the bowl sliding around.
When the milk is well incorporated into the eggs, pour it all back into the remaining milk in the saucepan and return to a medium-high heat, whisking constantly until the mixture is bubbling gently and is thick enough to coat the back of a spoon, barely dripping off. This
will take 3–4 minutes.
Remove from the heat, continue to whisk for a minute more, then add the butter, stirring
until it is melted into the crème pâtissière. Remove the vanilla pod, if you used one. Pour
the crème pâtissière into a bowl, allow to cool briefly, then cover the surface with cling film
(to prevent a skin forming) and refrigerate until needed. Use within a week.
Cardamom Creme Patissiere:
Add 10 bruised cardamom pods to the milk, heat it slightly, then allow it to infuse for an hour. Continue as above, leaving the cardamom pods in the crème pâtissière,
but make sure you remove them before using in a recipe.
Mousseline Creme Patissiere:
Above recipe completely made, plus 250 g unsalted butter, softened. Take the cooled, set
crème pâtissière and beat it in a freestanding electric mixer with whisk attachment, or in a
mixing bowl with handheld electric whisk. Slowly add the softened butter a little at a
time, and continue whisking until all the butter is incorporated and the mixture is smooth.
Recipe reprinted with permission of John Whaite.