Line an 8x8x2-inch pan with aluminum foil, extending the foil over the edges of the pan. Spray the foil with nonstick cooking spray; set aside.

In a large heavy saucepan, bring the sugar, butter, and eggnog to a full boil over medium heat. Continue to boil for 8 to 10 minutes, stirring constantly to prevent scorching.

Remove from heat and stir in the white chocolate chips and the grated nutmeg, stirring until the chocolate is melted.

Add marshmallow cream and rum extract; beat until well blended.

Immediately pour into a prepared pan and allow to cool completely at room temperature. Dust with nutmeg if desired, and cut into squares.

Store in an airtight container in the refrigerator. May be frozen for up to three weeks.