01 - Line an 8x8-inch baking pan with parchment paper, ensuring enough overhang for easy removal.
02 - In a medium saucepan over medium heat, melt the butter with eggnog and sugar, stirring frequently until the mixture just begins to boil.
03 - Reduce heat to low and simmer for 4 to 5 minutes, stirring constantly to prevent scorching.
04 - Remove from heat. Add white chocolate chips, ground nutmeg, ground cinnamon, and vanilla extract. Stir thoroughly until the chocolate is fully melted and the mixture is smooth.
05 - Immediately pour the mixture into the prepared pan. Smooth the surface with a spatula and sprinkle with freshly grated nutmeg if desired.
06 - Let cool at room temperature for 30 minutes, then refrigerate for at least 2 hours or until firm.
07 - Lift out the set fudge using the parchment overhang. Cut into 36 even squares with a sharp knife.