01 - Line an 8x8-inch baking pan with parchment paper, leaving an overhang to facilitate easy removal.
02 - In a medium saucepan over medium heat, combine unsalted butter, eggnog, and granulated sugar, stirring frequently until the mixture reaches a gentle boil.
03 - Reduce the heat to low and simmer the mixture for 4 to 5 minutes, stirring constantly to prevent scorching.
04 - Remove the saucepan from the 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 smooth.
05 - Pour the warm fudge mixture into the prepared baking pan, smoothing the surface with a spatula.
06 - Dust the top evenly with freshly grated nutmeg, if desired.
07 - Let the fudge cool at room temperature for 30 minutes, then transfer to the refrigerator and chill for at least 2 hours or until set.
08 - Using the parchment overhang, lift the fudge from the pan. Cut into 36 even squares with a sharp knife.