1-In a saucepan bring milk, vanilla, and: In a saucepan bring milk, vanilla, and salt to a simmer over medium heat. Do not boil the milk as it can overflow the pan and also overcook the eggs when tempering.
2-In a separate bowl, whisk together the: In a separate bowl, whisk together the egg yolks, sugar, cornstarch. It should be thick, creamy, and pale yellow.
3-While whisking, slowly add ½ cup of: While whisking, slowly add ½ cup of the hot milk mixture to the egg yolk mixture to temper it. This insures that the eggs don’t overcook and curdle.
4-Add the remaining milk mixture half a: Add the remaining milk mixture half a cup at a time, while continuously mixing.
5-Return to saucepan and cook over medium: Return to saucepan and cook over medium low to medium heat until the mixture is thick and bubbling. Remove from heat once the mixture boils.
6-If adding butter, add one tablespoon at: If adding butter, add one tablespoon at a time and mix until fully incorporated before adding the next. Sometimes the butter separates a bit and makes the mixture greasy. If this happens, whisk continuously for a few minutes until it’s fully combined and cooled down a bit. It should recombine and no longer be greasy.
7-Once everything is fully combined and slightly: Once everything is fully combined and slightly cooled but still warm, pour the mixture through a fine mesh strainer into another bowl. This will make for a very smooth pastry cream.
8-Cover with plastic wrap, placing the wrap: Cover with plastic wrap, placing the wrap directly on top of the pastry cream filing so it doesn’t get a film on top.
9-Then chill until ready to use, at: Then chill until ready to use, at least two hours or overnight.