Melt 8 tablespoons of unsalted butter in a saucepan over medium-high heat. Once melted, reduce heat to low and cook for 4-5 minutes until golden brown and nutty. Remove from heat, stir in 1 tablespoon of butter, and let cool for 10 minutes.

In a medium bowl, whisk together 2 cups of all-purpose flour, 1 teaspoon of baking soda, and 0.5 teaspoon of kosher salt.

In the mixing bowl with cooled brown butter, whisk together 1 cup of dark brown sugar and 0.5 cup of granulated sugar until smooth. Add 2 tablespoons of corn syrup and 2 teaspoons of vanilla extract, and mix until combined. Then, add 1 egg and whisk until glossy.

Fold the dry flour mixture into the wet mixture until just combined. Add 1.5 cups of chocolate chunks and 1 cup of toasted pecans, folding to distribute evenly.

Cover the dough and refrigerate for at least 2 hours, preferably 24 hours.

Preheat oven to 350°F (175°C). Line baking sheets with parchment paper. Portion chilled dough onto sheets, spacing 2 inches apart.

Bake for 10-12 minutes until edges are golden brown but centers remain slightly pale.

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