Make the eggnog cookies:

1. Preheat oven to 350°F and prepare 3 half sheet baking pans with parchment paper (or one, if working in batches).
2. In a large mixing bowl, add flour, baking soda, baking powder, salt, nutmeg, and cinnamon. Whisk well to combine, then set aside.
3. In another large mixing bowl, add melted butter, brown sugar, white sugar, eggnog, egg yolks, and vanilla. Beat with a hand mixer or whisk until well combined and smooth.
4. Add the dry ingredients to the wet ingredients and mix on low speed until combined, scraping down the edges of the bowl. Ensure the batter is well combined, but do not overmix. 
5. Using your hands or a cookie scoop, scoop 2 tablespoons of cookie dough. Place the cookie balls evenly onto the baking sheets, spacing them 2-3 inches apart (I do about 6 per sheet).
6. Place the cookies into the oven and bake for 11-13 minutes, until the edges are set. Allow the cookies to cool on baking sheet for 10 minutes before transferring onto a wire rack to fully cool before glazing.

Make the eggnog glaze:

1. Add all of the ingredients (confectioners' sugar, eggnog, and nutmeg) to a medium mixing bowl and whisk until smooth.
2. Using a spoon, drizzle the glaze over the cooled cookies. Allow the glaze to set for an hour before enjoying.