1. Line an 8×8-inch baking dish with parchment paper, leaving overhang on the sides for easy removal. Lightly grease if desired.

2. In a medium saucepan over low heat, melt the white chocolate and butter, stirring constantly until smooth.

3. Add the sweetened condensed milk and eggnog to the melted chocolate mixture. Stir until fully combined and glossy.

4. Remove from heat and stir in vanilla extract, ground nutmeg, and salt if using. Mix until evenly blended.

5. Pour the mixture into the prepared pan and smooth the top with a spatula. Tap gently to remove air bubbles.

6. Refrigerate for at least 4 hours or overnight until fully set.

7. Lift the fudge from the pan using the parchment edges. Slice into small squares with a sharp knife, wiping clean between cuts.