Place 2 cups of whole milk in a medium saucepan over medium high heat, stirring consistently and as soon as the milk begins to boil, remove from saucepan from the heat
In a large bowl, combine sugar, cornstarch and salt
Whisk in 4 egg yolks until everything is well combined and smooth
Slowly drizzle the hot milk into the whipped yolks, stirring constantly, until everything is fully combined
Pour the mixture back into the saucepan and return it to the stovetop over medium high heat until it begins to gently boil
Whisk consistently until the sauce thickens into a pudding like consistency
Remove the pastry cream from heat and transfer it into a glass bowl
Whisk in the vanilla extract and 4 tablespoons of softened butter until the filling appears smooth and creamy
Cover with plastic wrap, gently pressing down so that the plastic wrap sits directly on top of the filling
Refrigerate the pastry cream until fully chilled