Combine the two ounces of Bailey’s Irish cream with the eggnog, milk, and espresso in a saucepan. Place the saucepan over medium heat and bring to a simmer.
To make Bailey’s whipped cream for garnish, combine half an ounce of Bailey’s Irish cream with heavy whipping cream and sugar. Whip the mixture until soft peaks form.
Pour the espresso into the mug, then add the hot milk mixture. Top the drink with Bailey’s whipped cream and a sprinkle of nutmeg.