01 - Line an 8x8-inch baking pan with parchment paper, allowing an overhang for easy removal.
02 - In a medium saucepan over medium heat, add 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 continuously to avoid scorching.
04 - Remove saucepan from heat. Add white chocolate chips, ground nutmeg, ground cinnamon, and vanilla extract. Stir until the chocolate is fully melted and mixture is smooth.
05 - Immediately pour the mixture into the prepared pan and smooth the surface with a spatula. If using, sprinkle freshly grated nutmeg evenly over the top.
06 - Allow to cool at room temperature for 30 minutes, then refrigerate for a minimum of 2 hours until fully set.
07 - Using the parchment overhang, lift the fudge from the pan. Slice into 36 even squares with a sharp knife.