01 - Line an 8x8-inch baking pan with parchment paper, leaving an overhang 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 simmer for 4 to 5 minutes, stirring constantly to prevent scorching.
04 - Remove saucepan from heat. Add white chocolate chips, ground nutmeg, ground cinnamon, and pure vanilla extract. Stir thoroughly until the chocolate is fully melted and the mixture is uniformly smooth.
05 - Immediately pour the fudge mixture into the prepared pan and smooth the surface with a spatula.
06 - Evenly sprinkle freshly grated nutmeg over the top, if desired.
07 - Allow to cool at room temperature for 30 minutes, then transfer to the refrigerator and chill for a minimum of 2 hours until firm.
08 - Using the parchment paper overhang, lift the fudge from the pan. Cut into 36 equal squares with a sharp knife.