Prepare the Coffee: Brew 1 cup of strong coffee or prepare 1-2 shots of espresso. Stir in the light brown sugar and vanilla extract until dissolved.
1 cup strong brewed coffee, 1 to 2 tablespoons light brown sugar, ½ teaspoon pure vanilla extract
Heat the Eggnog Mixture: In a small saucepan over medium heat, combine the eggnog, milk, and ground nutmeg. Heat until it begins to lightly simmer, then remove from heat.
½ cup eggnog, ½ cup milk, ⅛ teaspoon ground nutmeg
Froth the Eggnog Mixture: Use a milk frother, immersion blender, or whisk to froth the heated mixture until foamy.
Combine: Pour the frothed eggnog mixture over the prepared coffee. Stir gently to combine.
Optional Garnish: Top with whipped cream and sprinkle with ground cinnamon or nutmeg, if desired.