Notes: You can make this sauce up to 2 days ahead; cover and chill.
1. In a 3- to 4-quart pan over medium heat, stir milk and sugar often until mixture begins to bubble around edges of pan, 10 to 12 minutes. Remove from heat.
2. Whisk about 1/2 cup of the hot milk mixture into egg yolks, then pour mixture into pan and whisk to blend. Stir with a flexible spatula over medium-low heat until custard coats the spatula in a smooth, velvety layer, 10 to 14 minutes. Remove from heat and pour through a fine strainer set over a bowl. Set bowl in a container of ice water and stir often until cool. Stir in vanilla. Serve cool or cold.
Nutritional analysis per 1/4 cup.