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 vanilla extract. Stir until completely smooth and all chocolate is melted.
05 - Immediately pour the mixture into the prepared pan, smoothing the surface with a spatula.
06 - Sprinkle freshly grated nutmeg evenly over the surface if desired.
07 - Allow to cool at room temperature for 30 minutes, then transfer to the refrigerator for at least 2 hours, or until fully set.
08 - Lift the set fudge from the pan using parchment overhang. Slice into 36 equal pieces with a sharp knife.