Heat the Milk: In a medium saucepan over medium heat, combine the milk, sugar, and vanilla (if using a vanilla bean, split it open to release more flavor). Heat until hot but not boiling.

Prep the Egg Yolk Mixture: While the milk is heating, whisk the egg yolks and salt together in a mixing bowl until combined.

Temper the Egg Yolks: Gradually pour the hot milk mixture into the yolks, continuously whisking to prevent the eggs from cooking.

Cook the Custard: Return the mixture to the saucepan and cook over low heat. Stir constantly with a wooden spoon until the custard thickens enough to coat the back of the spoon, about 10 minutes.

Strain the Custard: Pour the custard through a fine-mesh sieve into a clean bowl to remove any egg cooked bits and vanilla pod pieces (if used).

Chill: Allow it to cool slightly, then cover the surface with plastic wrap (to prevent a skin forming) and refrigerate until chilled.