In a medium bowl, add the egg yolks and erythritol, then whisk until light and fluffy, about 3-5 minutes.

In a saucepan, combine almond milk (or coconut milk), heavy cream, cinnamon, and nutmeg. Heat over medium until simmering, about 5 minutes.

Slowly pour the hot milk mixture into the egg yolk mixture, whisking continuously for about 2 minutes.

Return the mixture to the saucepan and cook over medium heat for another 5-7 minutes, stirring constantly until thickened.

Once cooked, strain the mixture through a fine-mesh sieve into a clean bowl.

Stir in the vanilla extract, then cover and place in the refrigerator to chill for at least 2 hours.

Once chilled, give the eggnog a stir before serving. Pour into glasses and top with cinnamon or whipped cream if desired.