01 - Line an 8x8-inch baking pan with parchment paper, allowing an overhang for easy removal.
02 - In a medium saucepan over medium heat, combine unsalted butter, eggnog, and granulated sugar. Stir frequently until the mixture begins to boil gently.
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 vanilla extract. Stir until the chocolate is fully melted and the mixture is smooth.
05 - Transfer the fudge mixture into the prepared pan. Smooth the surface with a heatproof spatula.
06 - If desired, sprinkle the top evenly with freshly grated nutmeg.
07 - Allow the pan to cool at room temperature for 30 minutes, then refrigerate for a minimum of 2 hours until the fudge is fully set.
08 - Lift the fudge from the pan using the parchment overhang. Cut into 36 squares using a sharp knife.