Bring to a Simmer:
2 cups milk
1 T. sugar
1 vanilla bean, split and scraped
3/4 cup sugar
3 T. cornstarch
Pinch of salt
Beat, then Add Sugar Mixture:
4 eggs, room temperature
Whisk Hot Milk into Egg Mixture; Return to Pan and Cook until Thick. Off Heat, Add:
3 T. unsalted butter
1 T. light rum, optional
1 t. vanilla extract
1.Bring milk, sugar, and vanilla bean to a simmer in a large, heavy saucepan (the sugar helps prevent the milk from scorching); stir to dissolve sugar. Then whisk the 3/4 cup sugar, cornstarch, and salt in a small mixing bowl; set aside.
2.Meanwhile, in a large mixing bowl, beat the eggs with an electric mixer on medium speed until light, fluffy, and lemon-colored, about 3 minutes (or whisk about 5 minutes by hand). Then add in the sugar-cornstarch mixture.
3.Remove vanilla pod from milk. Whisk 1/2 cup hot milk into the egg mixture. Add the egg mixture back to the milk in the saucepan and cook over medium heat until thick, 5-8 minutes. Stir constantly to prevent scorching.
4.Lightly boil the filling 1 minute to eliminate starchy taste from the cornstarch. Off heat, add butter, rum, and vanilla; transfer to a bowl. Cover with plastic wrap, pressing it on the surface to prevent it from forming a skin. Chill.