In mixer on high speed, beat egg yolks and maple syrup until mixture is very pale, creamy and thick, about 3 - 4 minutes.
Empty the egg yolk mixture into a blender, and add the milk, cream, vanilla and spices.
Cover and blend at medium speed for 30 seconds.
Using mixer again on high speed, beat egg whites in a medium bowl until soft peaks form.
Gently fold into eggnog base.
Add spirits and bitters if desired. Garnish with fresh grated nutmeg.
Can be served immediately or chilled. Enjoy within 2-4 days.