For the Cookies:
Mix flour, baking powder, nutmeg, and cinnamon together in a bowl, set aside. Cream butter and sugar until light and fluffy.
Add egg yolks and vanilla.
Add eggnog and mix until smooth.
Add the flour mixture and mix until just combined.
Use an ice cream scoop to drop batter on parchment lined baking sheets.
Bake in a preheated 300 degree oven for 20 to 22 minutes.
Cool the cookies on a rack.
For the Glaze:
Make the glaze by whisking together powdered sugar and eggnog until smooth.
Drizzle the glaze over the cookies and grate nutmeg over the top of the cookies.