I'd rather call it "Vanilla Sauce" because a cream would be a little thicker - but that's what Jamie Oliver's recipe says, so be it.
It is a very fine, tasty and silky sauce - you can use it in many recipes - ice cream, puddings, cakes, etc.
I've been making it for a long time to make ice cream from it, but a small part is good to keep in the freezer to have a vanilla sauce on an apple / cheese cake at hand at any time.
Here is the source of the recipe, Jamie rules :)
Milk (and sweet cream) is boiled with 4 tablespoons of sugar and vanilla essence (pure vanilla).
After boiling, take the pan off the heat and let it penetrate the vanilla flavor with the milk for 10-15 minutes.
In a bowl, separate the yolks and add 2 tablespoons of sugar.
Beat them well.
Add 1 tablespoon of hot milk and mix well after each one.
This is how you incorporate all the milk.
Put this mixture on the fire and stir continuously.
Notice that very quickly the cream becomes a little thicker and shinier, sticking to the back of the spoon.
At this point, quickly take it off the fire!
If you hesitate, it will be cheese, but ... if it is still cheese - pass it through a sieve and you will repair it.
And ready, serve it hot and cold.
If you want to heat it, put it on the steam bath.
It goes well and frozen, so very practical.
Good appetite!