Step 1: Prepare the Dry Ingredients

1. In a medium bowl, whisk together the flour, baking soda, baking powder, nutmeg, cinnamon, and salt. Set aside.

Step 2: Cream the Butter and Sugars

1. In a large mixing bowl, beat the softened butter, granulated sugar, and brown sugar with an electric mixer on medium speed until light and fluffy (about 2-3 minutes).

Step 3: Add the Wet Ingredients

1. Beat in the egg, eggnog, vanilla extract, and rum extract (if using) until well combined. The mixture may look slightly curdled, but this is normal.

Step 4: Combine Wet and Dry Ingredients

1. Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined. Do not overmix.

Step 5: Chill the Dough

1. Cover the dough with plastic wrap and refrigerate for at least 30 minutes. Chilling the dough helps the cookies hold their shape and enhances their flavor.

Step 6: Preheat the Oven

1. Preheat your oven to 350°F (175°C). Line two baking sheets with parchment paper or silicone baking mats.

Step 7: Scoop and Bake

1. Using a cookie scoop or tablespoon, drop rounded balls of dough onto the prepared baking sheets, spacing them about 2 inches apart.
2. Bake for 10-12 minutes, or until the edges are set and the centers look slightly underbaked.

Step 8: Cool the Cookies

1. Allow the cookies to cool on the baking sheets for 5 minutes before transferring them to a wire rack to cool completely.

Step 9: Make the Eggnog Glaze (Optional)

1. In a small bowl, whisk together the powdered sugar, eggnog, and vanilla extract until smooth. Adjust the consistency by adding more powdered sugar or eggnog as needed.
2. Drizzle or spread the glaze over the cooled cookies and sprinkle with a pinch of nutmeg for a festive finish.