Preheat the oven to 350°F (175°C) and line two baking sheets with parchment paper.

In a large bowl, cream the softened butter and brown sugar together until light and fluffy.

Mix in the maple syrup, pumpkin puree, egg yolk, and vanilla extract until smooth and well combined.

In a separate bowl, whisk together the flour, cornstarch, baking soda, pumpkin pie spice, cinnamon, and salt.

Add the dry ingredients to the wet ingredients and stir just until combined. Do not overmix.

If desired, chill the dough for 20 to 30 minutes for thicker cookies.

Scoop tablespoon-sized portions of dough and roll lightly in granulated sugar if using. Place them 2 inches apart on the prepared baking sheets.

Bake for 10 to 12 minutes, until the edges are set and the centers still look slightly soft.

Let the cookies cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.