01 - Line an 8x8-inch baking pan with parchment paper, ensuring the edges overhang for easy removal.
02 - In a medium saucepan set over medium heat, combine unsalted butter, eggnog, and granulated sugar. Stir frequently until the mixture begins to gently boil.
03 - Reduce the heat to low and allow the mixture to simmer, stirring constantly, for 4 to 5 minutes.
04 - Remove the saucepan from heat. Add white chocolate chips, ground nutmeg, ground cinnamon, and pure vanilla extract. Stir thoroughly until the chocolate is melted and the mixture is smooth.
05 - Immediately pour the fudge mixture into the prepared baking pan and smooth the surface with a spatula.
06 - If desired, sprinkle the surface evenly with freshly grated nutmeg.
07 - Allow the fudge to cool at room temperature for 30 minutes. Transfer to the refrigerator and chill for at least 2 hours, or until completely set.
08 - Using the parchment overhang, lift the set fudge out of the pan. Slice with a sharp knife into 36 equal squares.