Start with separating egg yolks and egg whites. Keep egg whites covered in the refrigerator until use.
Add sugar to the egg yolks. Whisk until it is creamy and all the sugar has dissolved.
Stir in milk, cream, vanilla extract, salt, nutmeg, cinnamon to yolk and sugar mixture. Whisk well.
Stir in Bourbon. Mix well.
If serving the Eggnog later, Cover the milk and egg mixture with cling wrap and refrigerate it. Else proceed with the next step
Remove egg whites from the refrigerator. Whisk it until it has stiff peaks.
Slowly add 1 cup of the milk and egg mixture to egg whites. Fold it to the egg whites.
Add the rest of the milk mixture to egg whites and mix well.
Sprinkle some nutmeg and cinnamon while serving.
Cooked Eggs Method: Add milk, cream, nutmeg, cinnamon, and salt to a saucepan. Heat the mixture until it is hot but not boiling. In a bowl whisk egg yolks and sugar until creamy. Then take 1/2 cup of hot milk mixture and slowly whisk to egg yolks while stirring continuously with the other hand. (This process is called tempering the egg.) Slowly add the egg and milk mixture to the rest of the hot milk mixture and keep stirring continuously to prevent the egg from cooking. Let the mixture heat on a very low flame for a couple of minutes. It will start to thicken a little. Switch off the flame. Let the mixture cool down completely. Then stir in the alcohol.
The flavors really blend well when the eggnog is aged at least for a day in the refrigerator.
Adjust the amount of alcohol as per taste. It can be increased up to 1 cup. You can also use a blend of alcohols.
Whisking egg whites and adding to the egg mixture ensures your eggnog is extra creamy and it provides that layer of froth at the top that can't be ignored.