In a large bowl, whisk egg yolks until smooth.
Gradually add the sugar, whisking constantly until fluffy. Set aside.
In a heavy pan, combine the milk, cloves, and cinnamon.
Heat on medium heat until it just starts to bubble.
Remove from heat.
Temper the egg mixture by adding a ladle of hot milk mixture to the egg mixture while whisking constantly.
Repeat until about half of the milk has been added to the egg mixture.
Pour the tempered egg mixture back into the pan (that has the remaining milk).
Cook over medium heat, stirring constantly with a wooden spoon.
Cook until temperature reaches 160 or mixture coats the back of the spoon. Don't allow to boil, or it will curdle.
Remove from heat and stir in the cream.
Strain through a mesh sieve and allow to cool.
Stir in vanilla extract, nutmeg, and bourbon or rum (if desired).
If you you are adding egg whites, beat them with a electric mixer until soft peaks form.
Add a teaspoon of sugar and beat until stiff peaks form.
Fold eggwhites into eggnog.
Heat the combined eggnog and egg white mixture until it reaches 160°F.
Remove from heat and let cool.