01 - Line an 8x8-inch baking pan with parchment paper, allowing for an overhang to facilitate removal.
02 - In a medium saucepan over medium heat, combine the unsalted butter, eggnog, and granulated sugar. Stir regularly until the mixture reaches a gentle boil.
03 - Reduce 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 has fully melted and the mixture is smooth.
05 - Pour the mixture promptly into the prepared baking pan. Smooth the surface using a spatula.
06 - Evenly sprinkle freshly grated nutmeg over the top if using.
07 - Allow to cool at room temperature for 30 minutes, then refrigerate for at least 2 hours or until the fudge is completely firm.
08 - Carefully lift the fudge from the pan using the parchment overhang and cut into 36 squares with a sharp knife.