01 - Line an 8x8-inch baking pan with parchment paper, leaving an overhang on the edges for easy lifting.
02 - In a medium saucepan set over medium heat, combine unsalted butter, eggnog, and granulated sugar. Stir regularly until the mixture reaches a gentle boil.
03 - Reduce the heat to low and let the mixture 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 the chocolate is fully melted and the mixture is completely smooth.
05 - Immediately pour the fudge mixture into the prepared baking pan. Smooth the surface using a spatula. Sprinkle freshly grated nutmeg over the top, if desired.
06 - Allow the fudge to cool at room temperature for 30 minutes, then transfer to the refrigerator. Chill for at least 2 hours or until set.
07 - Using the parchment overhang, lift the fudge from the pan. Cut into 36 even squares with a sharp knife.