In a medium saucepan over low-medium heat add the whole milk. Let cook for a couple of minutes to warm it up - do not boil the milk.
Warm the Milk
in a medium bowl whisk together the egg yolks, corn starch, salt, and sugar. Whisk for two minutes, the mixture should be much lighter in color..
Mix the Dry Ingredients
Once the milk mixture is warmed slowly add a little bit to the egg mixture and whisk to combine. Then add all of the milk slowly and whisk to combine.
Add mixture back to the pot and cook for another couple of minutes. You want it quite thick, the mixture will "burp" bubbles will pop on the surface- this shows it is done.
Warm the Mixture
Take off the heat and immediately add the cold butter and vanilla bean paste or extract.
Add Vanilla & Butter
Make sure to scrape down the sides and fully combine.
Then pour into an air-tight container, place plastic wrap on top and push directly on top Chill in the fridge for at least two hours or up to three days. Rewhisk the pastry cream before serving.
Chill Pastry Cream