In a medium saucepan over medium heat, melt 1 ½ cups of unsalted butter, swirling often until it becomes a golden brown and smells nutty, about 5-7 minutes. Remove from heat and let the brown butter cool to room temperature.

In a separate bowl, whisk together 3 cups of all-purpose flour, 1 tablespoon of cornstarch, 2 ½ teaspoons of baking soda, and ¼ teaspoon of salt until thoroughly blended.

In a large mixing bowl, combine the cooled brown butter with ⅔ cup of packed light or dark brown sugar and ⅓ cup of granulated sugar, beating until creamy and smooth, about 2-3 minutes.

Add 2 large room temperature eggs and 1 ½ teaspoons of vanilla extract to the mixing bowl. Beat until fully combined.

Gradually add the dry ingredients to the wet mixture, stirring gently until just combined.

Gently fold in 2 cups of chopped pecans into the cookie dough.

Cover the dough with plastic wrap and chill it in the refrigerator for at least 30 minutes.

Preheat your oven to 350°F (175°C) and prepare your baking sheets by lining them with parchment paper.

Roll approximately 2-tablespoon portions of dough into balls and place them on the prepared baking sheets about 2 inches apart.

Bake the cookies in the preheated oven for about 11 minutes, until the edges are golden and the centers remain soft.

Allow the cookies to cool on the baking sheets for about 5 minutes before transferring them to a wire rack to cool completely.