Line an 8 inch by 8 inch dish with parchment paper. Cut the corners of the parchment paper, then slide the cut ends behind one another to fit into the pan.
In a medium-sized saucepan add the butter, sugar, and eggnog. Bring this mixture to a boil over medium heat stirring constantly.
Insert a candy thermometer into the saucepan and bring the candy mixture to 230 degrees F. Stir constantly with a wooden spoon to keep the mixture from burning. This should take about 8-10 minutes.
Remove the saucepan from the heat and stir in the white chocolate and nutmeg and stir until the chocolate has melted.
Stir in the marshmallow creme and the rum extract until totally combined.
Pour the fudge mixture into the prepared pan and sprinkle with more nutmeg.
Let cool at room temperature for about an hour, then place the pan in the fridge overnight (7-8 hours) to set.
Remove the fudge from the pan by pulling up on the parchment paper and with a sharp chef's knife cut the fudge into 24 squares, or feel free to cut into smaller squares.
Store any leftover fudge in the refrigerator for up to 3 weeks.
Notes
You can freeze this fudge -
Fudge can be frozen for several months, just place the slices between pieces of parchment paper and store them in a freezer container.
When ready to serve, let the fudge defrost in the refrigerator for a couple of hours.
What kind of white chocolate can you use -
You can use white chocolate chips or you can chop up a white chocolate candy bar.