Whisk together the egg yolks and sugar in a medium bowl until light and creamy. Set aside.
Add the cream, milk, nutmeg, and salt into a saucepan, constantly stirring.
Slowly pour 1/2 cup of the hot milk to the egg mixture.* Vigorously whisk to avoid little bits of cooked egg.
Continue to do this until all the hot milk has been added to the eggs and the mixture is well combined.
Directly after the above step, pour the tempered egg mixture back into the milk saucepan on the stove.
Quickly whisk, and cook the mixture, stirring constantly, until it reaches 160 degrees on a thermometer.
Remove from the heat and stir in the vanilla.
Pour the eggnog into a bowl and cover with plastic wrap. Refrigerate until thoroughly chilled.
*This will temper the eggs so they don’t scramble when cooked on the stovetop