Preheat oven to 300 degrees. In a medium bowl, combine flour, baking powder, cinnamon and nutmeg. Mix well and set aside. In a large bowl, cream sugar and butter to form a grainy paste. Add eggnog, vanilla and yolks. Beat at medium speed until smooth. Add flour mixture and beat on low speed just until combined. Do not over mix.
Drop rounded teaspoonfuls onto a greased baking sheet one inch apart. Sprinkle lightly with nutmeg. Bake for 23-25 minutes or until bottoms turn light brown. Transfer to a wire rack immediately to cool. Yield: 3 dozen cookies.