01 - Line an 8x8-inch baking pan with parchment paper, allowing excess to hang over the sides for easy removal.
02 - In a medium saucepan over medium heat, combine unsalted butter, eggnog, and granulated sugar. Stir frequently until the mixture reaches a gentle boil.
03 - Reduce heat to low and continue simmering for 4 to 5 minutes, stirring constantly to prevent burning.
04 - Remove the saucepan from heat. Add white chocolate chips, ground nutmeg, ground cinnamon, and vanilla extract. Stir until the chocolate is fully melted and the mixture becomes smooth.
05 - Immediately pour the warm mixture into the prepared pan and use a spatula to smooth the surface.
06 - Evenly sprinkle freshly grated nutmeg over the surface, if desired.
07 - Allow the fudge to cool at room temperature for about 30 minutes, then refrigerate for at least 2 hours or until fully set.
08 - Using the parchment overhang, lift the fudge from the pan. Cut into 36 even squares with a sharp knife.