Line an 8x8 baking dish with parchment paper and spray lightly with cooking spray.
In a heavy saucepan, add the butter, eggnog, and sugar. Bring to a boil, then reduce heat to medium-high. Continue to boil until a candy thermometer temperature reaches 234°F. This takes about 10 minutes of stirring and boiling.
Remove from heat. Immediately add the white chocolate and stir until melted.
Stir in the marshmallow crème until completely combined.
Stir in the vanilla extract and ½ teaspoon of nutmeg. Leave the remaining ½ teaspoon of nutmeg for topping.
Spread evenly in the prepared baking dish. Sprinkled with the remaining ½ teaspoon nutmeg over top.
Chill in fridge at least 4 hours before cutting.
Notes
The parchment paper makes cleaning up a snap and makes it much easier to remove from your pan when it’s time to slice into squares.
You’ll need to stir the mixture constantly to prevent the sugar from burning.
Score the top of the fudge with a sharp knife before chilling to make cutting easier.