Line an 8×8-inch baking dish with parchment paper, leaving an overhang. Lightly grease the paper.

In a saucepan, combine butter, sugar, and eggnog. Bring to a gentle boil over medium heat, stirring often.

Reduce heat to low and cook for 10 minutes, stirring constantly.

Remove from heat and stir in the mini marshmallows until completely melted.

Add the white chocolate chips, vanilla extract, and ground nutmeg. Stir until smooth.

Pour the mixture into the prepared pan. Smooth the top.

Let it cool at room temperature for 1 hour, then refrigerate for at least 3 hours.

Slice into 36 squares and serve.