2 cups milk (whole milk is best)
1 tablespoon sugar
1 vanilla bean, split and scraped  

3/4 cup sugar
3 tablespoons cornstarch
Pinch of salt

4 large eggs, room temperature

3 tablespoons unsalted butter
1 teaspoons light rum, optional
1 teaspoon vanilla extract

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.

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.

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.

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 at least two hours, preferably overnight. 

From Cuisine Magazine