In a stand mixer with a wire whisk, beat the egg yolks until they lighten in color. Gradually add the ⅓ cup sugar and continue to beat until it is completely dissolved. Set aside.
Combine the milk, heavy cream and nutmeg in a medium saucepan over medium-high and bring just to a boil, stirring occasionally. DO NOT LET IT BOIL.
Remove from the heat and gradually temper the hot cream into the egg yolks/sugar. Do this by adding a SMALL amount of the hot cream to the eggs, whisking constantly. Continue adding hot cream to the eggs, whisking fast until the egg mixture is slightly warm. (note: if you mess up this step, you will have scrambled eggs floating in your eggnog)
Add tempered eggs to the rest of the cream mixture in the pot and cook & stir until it reaches 160 degrees F.
Remove from the heat, stir in the bourbon and pour into a medium mixing bowl. Set in the refrigerator to chill.
In a stand mixer with a clean wire whisk & bowl, beat the egg whites with a to soft peaks.
Gradually add the 1 tablespoon of powdered sugar and beat until stiff peaks form.
Whisk the egg whites into the chilled mixture.
Serve & Enjoy!