Mary Berry's proper custard
Bring the milk, cream and vanilla pod to simmering point slowly over a low heat.
Remove the vanilla pod (wash the vanilla pod, dry and store in jar with caster sugar to make vanilla sugar).
Whisk the yolks, sugar and cornflour together in a bowl until well blended.
Pour the hot milk and cream onto the eggs and sugar, whisking all the time with a balloon whisk.
Return to the pan, (add vanilla extract if using) and over a low heat gently stir with a wooden spatula until thickened.
Pour the custard into a jug and serve at once.
To keep hot, stand the jug in a pan of hot water and cover the top with cling film to prevent skin forming.
You can freeze the leftover egg whites for another time, or use them to make pavlovas, amaretti or macaroons. Homemade custard will keep in the fridge for up to 3 days.