Warm the milk in a medium saucepan over medium heat until tiny bubbles appear. Meanwhile, in a medium heatproof bowl, whisk the egg yolks and sugar until pale yellow. Add the cornstarch and salt and whisk well. Pour the hot milk into the yolk mixture, 1/2 cup at a time, whisking constantly. Return the mixture to the saucepan and cook over medium heat, whisking constantly, until it thickens to the consistency of thick pudding, about 2 minutes. (It will look lumpy as it starts to thicken but will smooth out as you continue to whisk.)

Remove from the heat and scrape the pastry cream into a large clean metal bowl. Whisk in the vanilla and then lay a sheet of plastic wrap directly on the surface. Refrigerate until thoroughly chilled, about 1 hour.

Make Ahead Tips: The pastry cream needs to chill for at least 1 hour before use and may be made ahead and refrigerated for up to a day.