In a large saucepan, combine the milk, cream, cinnamon, vanilla, and nutmeg. Bring to a boil over medium heat. Be careful when bringing to a boil that the milk doesn't boil over the pan. As soon as you see it bubbling, remove from heat.
3 cups whole milk, 1 cup heavy whipping cream, 4 cinnamon sticks, ¾ tablespoon pure vanilla extract, 1 teaspoon grated nutmeg
Allow to sit for at least 5-10 minutes to steep. (you want to make sure the milk mixture isn't hot enough to cook the eggs once added. So allow to sit for a little bit off the heat before the next step) :)
In the bowl of a stand mixer fitted with the paddle attachment, beat the eggs and sugar on medium-high/high until fully combined.
5 large eggs, ⅔ cup granulated sugar
Pour the egg mixture into the milk and whisk quickly until fully combined.
Add caramel, sea salt, and rum (if using). Continue whisking to fully combine.
½ cup caramel syrup, 1 tablespoon sea salt, ¾ cup dark rum
When you're ready to serve, beat the egg whites on high until foamy peaks form. (this is optional).
2 large egg whites*
Pour the eggnog into the glass leaving a bit of room at the top. Top with fluffy egg whites (optional)
Garnish with nutmeg and caramel sauce.