Whisk the egg yolks and sugar together in a medium bowl until light and creamy.

In a saucepan over medium-high 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 a minute or so, until the mixture is just slightly thickened (or until it reaches about 160 degrees F on a thermometer).

Remove from heat and stir in the vanilla, and alcohol*, if using.

Pour the eggnog through a fine mesh strainer into a pitcher or other container and cover with plastic wrap. Refrigerate until chilled.

Serve with a sprinkle of cinnamon or nutmeg, and fresh whipped cream, if desired.