Line a 8 or 9-inch square pan with foil and let it hang over the sides. Butter the foil.
In a heavy, 3-qt saucepan combine sugar, butter, and eggnog. Bring to a rolling boil, stirring constantly. Continue boiling 8-10 minutes over medium heat or until a candy thermemoter reaches 234 F, stirring constantly to prevent scorching. Remove from heat.
Using a wooden spoon, work quickly to stir in chopped white chocolate and nutmeg until chocolate is melted and smooth. Stir in marshmallow creme and rum extract. Beat until well blended and then pour into prepared pan. Sprinkle with a little freshly ground nutmeg on top. Let stand at room temperature until cooled. Refrigerate if you'd like to speed up the process.
When completely cool, cut into squares. Store in covered container.