Whisk the egg yolks and sugar together in a medium bowl until light and creamy.
In a saucepan over medium heat, combine the cream, milk, nutmeg and salt. Stir often until mixture reaches a bare simmer.
Add a big spoonful of the hot milk to the egg mixture, whisking vigorously. Repeat, adding a big spoonful at a time, to temper the eggs.
Once most of the hot milk has been added to the eggs, pour the mixture back into the saucepan on the stove.
Whisk constantly for just a few minutes, until the mixture is just slightly thickened (or until it reaches about 160 degrees F on a thermometer). It will thicken more as it cools.
Remove from heat and stir in 1 tsp vanilla if desired. (I think it makes it too sweet but this is different for everyone)
Pour the eggnog into a glass container with a lid.
Refrigerate until chilled. It will thicken as it cools.
Serve with a sprinkle of cinnamon or nutmeg, and fresh whipped cream, if desired.
Store homemade eggnog in the fridge for up to one week, and shake before you use.
