Place the yolks, sugar, cornstarch, and salt in a medium bowl and whisk to combine.

Heat the milk in a small pot until small bubbles form around the edge and wisps of steam are rising from the surface.

Add the hot milk to the egg mixture a little at a time, whisking to combine.

When all the milk has been added, transfer the mixture back to the pot and place over medium-low heat. Cook the pastry cream, whisking, until thickened.

Stir in the vanilla, and pour the pastry cream through a fine mesh strainer into a heat-safe bowl.

Use the back of a ladle to press the mixture through the sieve.

Press a layer of plastic wrap directly onto the surface, and refrigerate.