Active time: 20 minutes (plus 4 hours chill time)
2 cups skim milk
1/2 vanilla bean, split and scraped
2 large eggs plus 1 egg yolk
1/4 cup fat-free sweetened condensed milk
1/2 teaspoon cornstarch
1/4 teaspoon freshly grated whole nutmeg (plus more for garnish)
1/8 teaspoon salt
1/4 cup white rum or bourbon
In a medium saucepan, bring 1 1/2 cups of the milk and the vanilla bean pod and seeds to a simmer over medium heat. Meanwhile, whisk the eggs, egg yolk, condensed milk, cornstarch, nutmeg and salt in a medium bowl until light yellow.
Gradually pour the hot milk mixture into the egg mixture, whisking constantly, then pour it back into the pan. Stir constantly over low heat with a wooden spoon until the eggnog begins to thicken, about 10 minutes.
Remove from the heat and immediately stir in the remaining 1/2 cup of milk. Transfer the eggnog to a pitcher; cover and refrigerate for at least 4 hours or overnight.
Remove the vanilla pod.
Spike the eggnog with alcohol if desired, and garnish with freshly grated nutmeg.