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

2. In a large mixing bowl, beat the softened butter with 1 cup granulated sugar until pale and fluffy, about 2-3 minutes.

3. Add the egg yolk, eggnog, and vanilla extract to the butter mixture and beat until creamy and fully combined.

4. Gradually add the dry ingredients to the wet ingredients, mixing on low speed just until combined.

5. In a small bowl, mix 2 tablespoons granulated sugar with 1/2 teaspoon ground cinnamon for topping.

6. Scoop 1.5-tablespoon portions of dough and roll into balls, then roll each ball in the cinnamon-sugar topping.

7. Arrange dough balls 2 inches apart on a parchment-lined baking sheet.

8. Bake at 350°F (175°C) for 10–12 minutes, until edges are set but centers look slightly underbaked.

9. Cool on the baking sheet for 5 minutes, then transfer to a wire rack to finish cooling.