Prepare an ice bath by placing a quart-sized mason jar (or similarly-sized vessel) in a large bowl. Scoop ice around the mason jar and pour a small amount of water into the bowl.
In a medium pot, mix the milk, cream, vanilla bean, salt, and 1/2 cup sugar.
In a medium heat-safe bowl, whisk the remaining 1/2 cup sugar and egg yolks to combine.
Bring the milk mixture to a simmer over medium heat. Pour 1/3 of the warm milk mixture into the yolk mixture (to temper the eggs) and whisk constantly to combine.
Pour the yolk mixture back into the pot with the remaining 2/3 of the milk, whisking constantly to combine and prevent the eggs from scrambling.
Continue to cook over medium-low heat, stirring constantly, until the mixture is thick enough to coat the back of a spoon, 6 to 8 minutes. Strain the sauce into the mason jar and cool completely. Refrigerate until ready to use.
I always carry three kinds of hot sauce in my purse. I have a soft spot for making people their favorite dessert, especially if it's pie. My first cookbook, The Fearless Baker, is out on October 24, 2017.