Whisk together the egg yolks and granulated sugar until frothy. I suggest a mixer with a whisk attachment but you can whisk by hand.
Over low-medium heat, combine the milk, heavy whipping cream, nutmeg, and salt in a saucepan. Whisk together until hot and starting to steam – a light simmer. Do not boil or burn the milk.
Add 1 tablespoon at a time of the milk mixture to the egg mixture, whisking, until all of the milk as been added. Once incorporated, pour mixture back into the saucepan and whisk together until it begins to thicken. Once thick, remove from heat and stir in the vanilla. Adjust spices for taste preference.
Funnel the eggnog into a glass jar or pitcher and store in the fridge.
GubChef Tip: If you want a runnier eggnog, add more milk.