In a medium-sized mixing bowl, beat the egg whites with electric beaters until they start to thicken. Add the 1 cup sugar, and continue to beat until thick. The mixture should be thick, and fluffy, but to the point of reaching soft peaks yet. Set aside until ready to use.
In another medium-sized bowl combine the egg yolks and sea salt. Beat with electric beaters until smooth and slightly thickened. Set aside.
Then in a very large bowl(you’ll have close to 1 gallon of eggnog, so be sure to use the biggest mixing bowl you have!) Combine the heavy cream, vanilla extract, and the remaining 2 tbsp of sugar. Beat with electric beaters at high speed until the mixture starts to thicken. Be careful not to overbeat your heavy cream, you want the mixture to be thick, but you don’t want to make whipped cream!
While continuing to beat, carefully pour in the 7 cups of milk, followed by the spiced rum(if you are using it), and beat until smooth.
Then pour in both the egg white mixture and the egg yolk mixture and beat just until combined.
Transfer the finished eggnog to a large jar, bottle, or airtight container and place in the fridge to chill, about 2-4 hours
Serve your eggnog cold with a dusting of ground nutmeg or ground cinnamon. Enjoy!