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

2. In a large mixing bowl, beat the softened butter and granulated sugar until light and fluffy.

3. Add in the egg yolk, vanilla extract, and eggnog, and mix until smooth and combined.

4. Gradually add the dry mixture into the wet, stirring until just combined. Do not overmix.

5. Chill the dough in the refrigerator for at least 1 hour to firm up.

6. Preheat oven to 350°F (175°C) and line a baking sheet with parchment paper.

7. Scoop tablespoon-sized dough balls and place them 2 inches apart on the sheet.

8. Bake for 9–11 minutes until edges are set and centers look slightly soft.

9. Cool cookies completely on a wire rack.

10. For the glaze, whisk powdered sugar with eggnog until smooth.

11. Drizzle glaze over the cooled cookies and sprinkle lightly with nutmeg. Let glaze set before serving or storing.