01 - Line an 8x8-inch baking pan with parchment paper, leaving an overhang to assist with removal.
02 - Combine unsalted butter, eggnog, and granulated sugar in a medium saucepan over medium heat. Stir frequently until mixture reaches a gentle boil.
03 - Reduce to low heat 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 vanilla extract. Stir continuously until chocolate is melted and mixture is fully smooth.
05 - Promptly pour the fudge mixture into the prepared baking pan and smooth the top with a spatula.
06 - Sprinkle freshly grated nutmeg evenly over the top if desired.
07 - Cool at room temperature for 30 minutes, then refrigerate pan for at least 2 hours or until firm throughout.
08 - Using the parchment overhang, lift set fudge from the pan. Slice into 36 even squares with a sharp knife.