01 - Line an 8x8-inch baking pan with parchment paper, leaving an overhang for easy fudge removal.
02 - In a medium saucepan over medium heat, combine the unsalted butter, eggnog, and granulated sugar. Stir frequently until the mixture gently boils.
03 - Reduce heat to low and 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 pure vanilla extract. Stir until the chocolate is fully melted and the mixture is smooth.
05 - Immediately pour the fudge mixture into the prepared baking pan. Smooth the surface with a spatula.
06 - Sprinkle the top evenly with freshly grated nutmeg, if desired.
07 - Allow the fudge to cool at room temperature for 30 minutes. Refrigerate for at least 2 hours or until fully firm.
08 - Using the parchment paper overhang, lift the fudge from the pan. Cut into 36 even squares with a sharp knife.