Difficulty: Easy - for beginners
500ml/18fl oz milk
1 vanilla pod, split down the middle and seeds scraped out (or a dash of vanilla extract)
100g/3½oz caster sugar
4 free-range eggs, yolks only
Pour the milk into a pan and add the split vanilla pod and its seeds. Bring the milk mixture to the boil, then remove from the heat.
Whisk the sugar, egg yolks and cornflour together in a large bowl.
Pour out a little of the hot milk onto the egg mixture, whisking continuously. Whisk in the rest of the hot milk until well-combined, then return to the pan.
Cook the mixture over a gentle heat, stirring continuously, until the mixture becomes thick. It will just come to the boil.
Remove from the heat and pass the mixture through a sieve into a clean bowl. Add the butter and stir until melted and thoroughly combined.
Leave to cool, cover with clingfilm and then chill before using.