Preheat your oven to 350°F (175°C). Butter the bottoms and sides of 2 small ramekins.

In a medium bowl, beat the egg until well combined and frothy. Gradually mix in the eggnog, granulated sugar, brown sugar, and nutmeg until smooth.

Heat a cup of water in the microwave for 2 minutes to create a hot water bath in a baking dish.

Pour the custard mixture into the prepared ramekins just below the rim and place them in the baking dish surrounded by hot water.

Bake for 30 to 35 minutes until set and a knife inserted comes out clean.

Let the ramekins cool at room temperature for about 15 minutes before serving with a sprinkle of nutmeg.