01 - Line an 8x8-inch baking pan with parchment paper, allowing extra parchment to extend over the edges for easy removal.
02 - In a medium saucepan, combine unsalted butter, eggnog, and granulated sugar over medium heat. Stir frequently until the mixture reaches a gentle boil.
03 - Lower the heat and simmer for 4 to 5 minutes, stirring constantly to avoid scorching.
04 - Remove the saucepan from heat. Immediately add white chocolate chips, ground nutmeg, ground cinnamon, and pure vanilla extract. Stir until the chocolate is fully melted and the mixture is smooth.
05 - Pour the smooth fudge mixture into the prepared pan. Use a spatula to even out the surface.
06 - Evenly sprinkle freshly grated nutmeg over the top if desired.
07 - Let the fudge rest at room temperature for 30 minutes. Transfer to the refrigerator and chill for at least 2 hours, or until set.
08 - Lift the firm fudge from the pan using the parchment overhang. Cut into 36 squares using a sharp knife.