1. In a medium saucepan, combine the milk and half of the sugar. Heat over medium heat until just simmering, then remove from the heat.

2. In a separate bowl, whisk together the egg yolks, remaining sugar, cornstarch, and salt until smooth.

3. Gradually pour a small amount of the hot milk into the egg mixture to temper it, whisking continuously.

4. Slowly whisk the tempered mixture back into the saucepan with the remaining milk.

5. Return the saucepan to medium heat and cook, stirring constantly, until the mixture thickens and comes to a boil (about 3-5 minutes).

6. Once thickened, remove from heat and stir in the butter and vanilla extract until fully incorporated.

7. For an extra-smooth finish, strain the pastry cream through a fine sieve into a clean bowl.

8. Cover the surface directly with plastic wrap to prevent a skin from forming and allow it to cool completely.