Pour the milk into the saucepan and warm to the point just before it boils. If you are using vanilla beans, add to the milk before heating.
Mix the egg yolks and sugar together in a bowl, and then mix in the cake flour.
Stir the milk into the bowl in small batches. Strain, and then return the mixture to the saucepan.
Mix over a medium heat until it has slightly thickened, then remove from the heat. Add the vanilla essence (or liqueur), and then transfer it to a bowl to cool.
When letting it cool, wrap it tightly with plastic wrap. It will go bad if moisture is allowed to build up.
If you want to chill it quickly, spread it out in a large container and chill it with an ice pack as shown in the photo.
Story Behind this Recipe
Delicious custard cream is essential if you are going to make cream puffs! I add the same amount of heavy cream to this custard cream, and use it when I'm making cream puffs.
It will harden when chilled, so don't heat too much. Stop the heat when it has softened a little. Use any kind of liqueur you like. You can easily make custard cream in the microwave, but I think making it in a saucepan gives a smoother and tastier finish.