In a medium bowl, whisk together the egg yolks and sugar until the mixture becomes light and creamy.
On the stovetop, warm the cream, milk, nutmeg, and a pinch of salt in a saucepan over medium heat. Stir gently until the mixture just begins to simmer.
To temper the eggs, take a generous spoonful of the warmed milk and whisk into the egg mixture. Repeat this process, one spoonful at a time, until all the milk has been blended in.
Pour the tempered egg mixture back into the saucepan, and return it to the stove over medium heat. Whisk constantly for about a minute, just until it thickens slightly or reaches 160°F.
Remove the saucepan from the heat and stir in the vanilla.
Strain the eggnog through a fine mesh sieve into a mason jar, then cover and refrigerate until chilled and velvety. If a thinner consistency is preferred, blend with a tablespoon or two of milk before serving.
To serve, pour into glasses and top with a sprinkle of nutmeg or cinnamon, and perhaps a dollop of whipped cream. Enjoy!
