Add egg yolks to a large bowl and beat until they become lighter in color. Then, gradually add sugar.
If you want a fluffier texture, add egg whites to a separate bowl and beat to soft peaks. Gradually add the remaining one tablespoon of sugar. Then, whisk the egg whites into the egg yolks, and set aside.
Add milk, heavy cream, and nutmeg to a saucepan and place over high heat. Stir occasionally until boiling.
Remove the saucepan from the heat, then gradually temper the hot milk mixture into the eggs. Put the saucepan back onto the stove and cook until it reaches 160°F.
Remove the mixture from the heat. If you’re making a spiked version, add the bourbon.
Let the mixture rest in the fridge; however, do not put it in the fridge if it’s still piping hot, as it can spoil your food. Enjoy your eggnog once it’s cold.