Preheat oven to 300 degrees F.

In a large bowl, with a hand mixer cream sugar and butter until light and fluffy.

Add eggnog, vanilla, and egg yolks. Beat at medium speed until smooth.

Add the flour mixture and mix at low speed just until the ingredients are combined. This can also be done by hand with a large mixing spoon. Do NOT over mix.

Spoon onto ungreased cookie sheets or parchment paper lined cookie sheets. Make the dough balls small; I used a small cookie scoop to form each ball. The dough spreads when quite a bit when cooked, so only put 12 cookies per cookie sheet.

Sprinkle a little nutmeg on each dough ball. Bake 15-18 minutes or until the edges barely start to brown. Do not over-cook.

Meanwhile, prepare the eggnog glaze. Mix the powdered sugar and eggnog together in a small bowl.

Drizzle warm or cool cookies with glaze. Sprinkle lightly with cinnamon. I put the cookies on a wire cooling rack with the rack placed over parchment paper to catch the drips from the glaze.