01 - Line an 8x8-inch baking pan with parchment paper, leaving an overhang on two sides for easy removal.
02 - In a medium saucepan over medium heat, combine unsalted butter, eggnog, and granulated sugar. Stir frequently until the mixture comes to a gentle boil.
03 - Reduce heat to low and simmer for 4 to 5 minutes, stirring constantly to prevent scorching.
04 - Remove pan from heat. Add white chocolate chips, ground nutmeg, ground cinnamon, and vanilla extract. Stir until the chocolate has melted completely and the mixture is smooth.
05 - Immediately pour the mixture into the prepared pan, smoothing the top with a spatula.
06 - Sprinkle the surface evenly with freshly grated nutmeg, if desired.
07 - Allow the fudge to cool at room temperature for 30 minutes, then refrigerate for at least 2 hours or until fully set.
08 - Use the parchment overhang to lift out the fudge. Slice into 36 even squares with a sharp knife.