Brew a strong cup of coffee or pull two shots of espresso.
Heat eggnog in a small saucepan on medium-low, stirring until warm but not boiling.
Pour hot coffee into a mug, then add in the warmed eggnog.
If using rum and sugar, stir them in until dissolved.
Top with whipped cream if desired.
Sprinkle ground nutmeg over the top for garnish.
Serve immediately while hot.
Notes
Freshly grated nutmeg offers a much better aroma than pre-ground. For a stronger coffee flavor, use espresso instead of drip coffee. Rum is optional for a non-alcoholic version. Homemade eggnog adds richness but store-bought works perfectly.