Preheat the oven to 375°F and line a baking sheet with parchment paper.

Brown the butter by melting it in a skillet over medium heat. Whisk it continuously as it foams until brown flecks appear, and a nutty aroma develops—about 4-5 minutes. Once done, remove it from heat.

Measure the brown butter and pour it into a measuring cup, aiming for about 1/2 cup.

In a mixing bowl, whisk the browned butter with granulated sugar and brown sugar until the mixture becomes light and fluffy (about 3-4 minutes).

Reduce the mixer speed and mix in vanilla extract, then the egg, until fully combined.

Fold in the flour, baking powder, baking soda, and kosher salt until just incorporated. Be careful not to overmix; this ensures a tender cookie.

Gently fold in the chocolate chips and chopped pecans until they are evenly distributed.

Use a cookie scoop to form scant 1/4-cup balls for large cookies or 2-tablespoon balls for smaller ones, leaving 2 inches between dough balls on the baking sheet.

Refrigerate the dough on the baking sheet, covered loosely, for at least 1 hour (up to 48 hours) to enhance the caramel flavor and control spread.

Bake one tray in the middle of the oven for 10-12 minutes, until the edges are deep golden brown and the tops are lighter. Add 1-2 minutes for crisper cookies.

Allow the cookies to cool on the sheet until set, sprinkling with flaky sea salt if desired.

Repeat with the remaining dough.