Preheat oven to 300 degrees. In a bowl, combine all the dry ingredients together. In a large bowl, cream together the sugar and butter until it resembles a grainy paste. Add eggnog, vanilla and egg yolks and beat at medium speed until smooth. Add the flour mixture and beat at low speed until blended. Do not over mix. Drop by teaspoons onto ungreased baking sheet, 1 inch apart. Sprinkle lightly with additional nutmeg. Bake for 23-25 minutes or until bottoms turn light brown. Transfer from pans immediately to cool.