Whisk together the eggs, milk, maple syrup, nutmeg, and salt in a large saucepan or Dutch oven.
Cook over low heat, stirring constantly, until the mixture thickens and will coat a spoon, about 1 hour (my kids like to take turns stirring, which they enjoy--and it usually doesn't take quite an hour).
Remove pan from heat, pour the mixture into a bowl, and then add the vanilla, stirring to combine. Refrigerate for several (2-3) hours, or until chilled.
After eggnog is chilled, whip the heavy cream. To whip the cream, put it in the bowl of a stand mixer (or a large mixing bowl) and beat until soft peaks form. Fold the whipped cream into the chilled eggnog. Garnish with a few shakes of nutmeg or cinnamon.