01 - Line an 8x8-inch baking pan with parchment paper, leaving an overhang for easy removal.
02 - In a medium saucepan, combine unsalted butter, eggnog, and granulated sugar over medium heat, stirring frequently until the mixture reaches a gentle 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 glossy and smooth.
05 - Immediately transfer the mixture into the prepared pan and smooth the surface with a spatula. Sprinkle freshly grated nutmeg over the top for garnish if desired.
06 - Allow to cool at room temperature for 30 minutes, then refrigerate for a minimum of 2 hours or until fully set and firm.
07 - Remove the set fudge from the pan using the parchment paper overhang. Slice into 36 equal squares using a sharp knife.