In a small bowl, combine the cinnamon and nutmeg. Reserve ¼ teaspoon for the topping and set aside.
Prepare a 9-inch square baking dish by lining with parchment paper. Set aside.
In a large saucepan, melt the butter with sugar, eggnog, and salt over medium high heat. Bring to a boil. Stirring continuously until the mixture reaches a rolling boil for four minutes. (Soft ball stage- 237 to 239 °F).
Remove the mixture from heat. Using an electric mixer and mix with the salt, marshmallow cream, white chocolate chips and 1/4 teaspoon of the spice mixture on medium speed until smooth and white chocolate is completely melted. Pour into the prepared baking dish.
Sprinkle the remaining ¼ teaspoon of the spices over the fudge.
Place the fudge on an even surface for about 4 hours to set.
Use a warm, clean knife to slice the fudge for serving.
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