1. In a large mixing bowl, cream together the softened butter and granulated sugar using a hand or stand mixer until light and fluffy (about 2–3 minutes).

2. Add the egg yolk, eggnog, and vanilla extract to the bowl. Beat until well combined.

3. In a separate bowl, whisk together the flour, baking powder, and salt.

4. Gradually add the dry mixture to the wet ingredients, stirring just until a dough forms. Do not overmix.

5. (Optional) Chill the dough in the refrigerator for 30 minutes for thicker cookies and reduced spreading.

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

7. Scoop tablespoon-sized portions of dough onto the prepared sheet. Slightly flatten each with your fingers or the back of a spoon.

8. Sprinkle each cookie with a pinch of ground nutmeg.

9. Bake for 10–12 minutes, or until the edges are just golden.

10. Let cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.