In a medium saucepan, whisk together the milk, sugar, and salt.

Place the saucepan over medium heat and stir frequently until the mixture is hot but not boiling.

In a separate bowl, whisk the egg yolks until they are pale and frothy.

Gradually add a small amount of the hot milk mixture to the egg yolks, whisking constantly.

Slowly pour the tempered egg yolk mixture back into the saucepan with the remaining milk mixture.

Continue heating the saucepan over medium-low heat, stirring constantly until the custard thickens enough to coat the back of a spoon.

Once thickened, remove the custard from heat and stir in the vanilla extract and cornstarch.

If desired, strain the custard through a fine mesh strainer into a bowl.