Step 1

In a large saucepan, combine the milk, vanilla pod and scrapings, and allspice. Heat over a medium flame, swirling occasionally, until bubbles form around the sides and the milk is steaming. Cover and steep for 20 - 30 minutes.

Step 2

Place the heavy cream and nutmeg in a large bowl or measuring cup and place a fine-mesh strainer over the top.

Step 3

In another large bowl or in the bowl of stand mixer fitted with the whip attachment, vigorously beat together the eggs, egg yolks, sugar, and salt with a sturdy wire whisk until thickened and pale, 3 - 5 minutes. This helps the eggnog cook faster and gives it a thicker, more voluptuous mouthfeel.

Step 4

When the milk has finished steeping, heat it again until steaming, then slowly dribble the hot milk into the eggs, whisking constantly. Return the mixture to the pot and cook over medium-low heat, stirring constantly with a heat-proof silicone spatula, until the mixture reaches 165º on an instant-read thermometer, 3 - 5 minutes. (Or, if your milk was hot enough, you may not need to cook it at all.) Immediately strain the milk mixture into the heavy cream.

Step 5

Chill the mixture over an ice water bath until cold, then stir in the brandy (if using) and refrigerate until thoroughly chilled, at least one hour and up to 3 days.

Step 6

To serve, pour into small glasses and grate a bit of fresh nutmeg over the top.