Cremè partissierè

In a mixing bowl add the egg yolk sugar and vanilla whisk continuously till the mixture is pale yellow and increases in volume

In a pot add the cream or milk or half and half and bring it to a simmer (not boil) remove the pot from the stove and take like 1/2 cup of the warm milk and start adding it slowly to the whisked egg yolks while whisking the mixture continuously( this process is called tampering ie to rise the temperature of the yolks so as to prevent it from scrambling whilst cooking.

Next add the yolks mixture to the remaining cream and bring the mixture to a boil (cook until it costs the back of a wooden spoon)

Whisk in the butter and set aside.

To store the custard cover it with plastic wrap making sure it directly touches the custard so as to prevent skin from forming on top of the custard.