Line a 9"x13" inch pan with non-stick foil; set aside.
In a large, heavy saucepan, combine sugars, butter, eggnog, marshmallows and salt.
2 cups sugar, 2 cup packed brown sugar, 16 tablespoon unsalted butter, 10 ounce marshmallows, 1/2 teaspoon salt, 1 1/8 cup eggnog
Bring to a rolling boil, stirring constantly. Continue boiling and stirring until a candy thermometer reads 238°F.
Remove from heat. Using an electric mixer immediately beat in white chocolate, vanilla and nutmeg until well blended. Continue beating while the mixture cools slightly and begins to thicken and hold trails and ridges in the surface for a few seconds.