01 - Line an 8x8-inch baking pan with parchment paper, ensuring the paper overhangs 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 the heat to low and continue to simmer for 4 to 5 minutes, stirring constantly to prevent scorching.
04 - Remove the saucepan from heat. 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 - Immediately transfer the prepared mixture into the lined baking pan. Smooth the surface with a spatula.
06 - Sprinkle freshly grated nutmeg over the top if desired.
07 - Allow the fudge to cool at room temperature for 30 minutes, then refrigerate for a minimum of 2 hours until firm.
08 - Using the parchment overhang, lift the set fudge from the pan. Cut into 36 even squares with a sharp knife.