01 - Line an 8x8-inch baking pan with parchment paper, leaving an overhang to facilitate removal.
02 - In a medium saucepan over medium heat, combine unsalted butter, eggnog, and granulated sugar. Stir frequently until mixture reaches a gentle boil.
03 - Reduce heat to low and simmer for 4 to 5 minutes, stirring constantly to avoid scorching.
04 - Remove saucepan from heat. Add white chocolate chips, ground nutmeg, ground cinnamon, and vanilla extract. Stir steadily until the chocolate is melted and mixture achieves a smooth consistency.
05 - Immediately transfer mixture into prepared pan. Use a spatula to smooth the surface evenly.
06 - Evenly sprinkle freshly grated nutmeg over the surface, if desired.
07 - Allow to cool at room temperature for 30 minutes, then refrigerate uncovered for a minimum of 2 hours or until fully set.
08 - Use parchment overhang to lift fudge from pan. Cut with a sharp knife into 36 equally-sized squares.