In a medium mixing bowl, whisk together the egg yolks and sugar until the mixture becomes thick and pale yellow. Set aside.
Heat the milk mixture
In a medium saucepan, combine the heavy cream, milk, nutmeg, cinnamon, and salt. Cook over medium heat, stirring often, until the mixture reaches a light simmer. Do not boil. Reduce the heat to low.
Temper the eggs
To avoid scrambling the yolks, slowly whisk in about 1 tablespoon of the hot milk mixture into the egg yolks. Continue gradually adding about ¼ cup at a time, whisking constantly, until most of the hot liquid is incorporated.
Thicken the eggnog
Pour the tempered egg mixture back into the saucepan. Cook over medium-low heat, whisking constantly, until the mixture has slightly thickened and reached 160°F on a thermometer. Do not let it boil.
Add vanilla and chill
Remove from the heat and stir in the vanilla extract. Pour the eggnog into a pitcher and refrigerate for at least 1 hour, or until thoroughly chilled.
Serve
Pour the chilled eggnog into cups. Top with whipped cream, a sprinkle of cinnamon or nutmeg, and garnish with a cinnamon stick for that festive touch.
Notes
Storage (in refrigerator):Store the eggnog in a sealed pitcher or container. It’s best consumed within 3–4 days. After that, flavors may degrade, and the texture can become loose.Freezing / thawing:I don’t typically recommend freezing eggnog because custard mixtures often separate or become grainy upon thawing. If necessary, freeze in small portions and thaw slowly in the refrigerator; then whisk well before serving.Make-ahead:You can prepare the eggnog base up to a day ahead. After cooking and straining, cool it to room temperature, then refrigerate overnight. Add whipped cream and any garnish just before serving.
Variations & Enhancements
Egg white foam: For a frothy top, beat the reserved egg whites until soft peaks form and fold them in just before serving.
Spice twist: Try adding a pinch of ground cloves, allspice, or even cardamom for a more exotic note.
Vanilla bean upgrade: Use ½ vanilla bean (split & scraped) instead of extract for a more seductive vanilla layer.
Lighter version: Use part milk or half-and-half in place of some heavy cream. It won’t be as rich, but it will still be tasty.
Spiked version: Add ¼ to ½ cup of bourbon, rum, brandy, or a mix (adjust according to your crowd’s needs).