Preheat the oven to 300°F (149°C). Toast the chopped pecans on a large baking sheet lined with parchment paper for 15 minutes, stirring twice. Turn the oven off and set the pecans aside.

In a large bowl, beat the softened butter on medium speed until smooth and creamy. Add granulated sugar and brown sugar, beating until fluffy and light in color. Incorporate eggs and vanilla, mixing on high speed. Scrape down the bowl as needed.

In a separate bowl, whisk together all-purpose flour, cornstarch, baking soda, and salt. Gradually add to the wet ingredients on low speed until combined. The cookie dough will be thick. Fold in the toasted pecans and mix briefly.

Cover the dough tightly with aluminum foil or plastic wrap and chill for at least 3 hours, or up to 3 days.

Remove the dough from the refrigerator and let it sit at room temperature for 20-30 minutes before baking.

Preheat the oven to 350°F (177°C) and line two baking sheets with parchment paper or silicone mats.

Once the dough is chilled, scoop and roll into balls, about 1 tablespoon each. Optionally, roll the balls in granulated sugar before baking.

Bake for 11-12 minutes (13 for crispier cookies) until golden brown around the edges. Let cool for 5 minutes on the cookie sheet before transferring to a cooling rack.