In a medium bowl, combine the flour, baking powder, baking soda, and salt. Set aside.

Brown the butter: In a small saucepan, add 213g (15 tbsp) of unsalted butter and place over medium heat. As the butter melts, stir it with a rubber spatula to encourage even cooking. Once the butter has fully melted, it will alternate between rapid large bubbles and gentle small foamy bubbles. The butter will be ready once it turns a dark golden color and the fat solids have darkened and settled at the bottom of the pan. Immediately pour into a medium bowl, scraping out the fat solids at the bottom, and weigh out to 170g (¾ cup).

Place the brown butter in the freezer for about 30 minutes, stirring every 10 minutes until solidified, yet soft.

In the bowl of a stand mixer fitted with the paddle attachment, cream together the solidified brown butter and sugars for 2-3 minutes until light & fluffy. Mix in the egg and vanilla until fully combined.

Add the dry ingredients and mix on low speed until mostly combined.

Lastly, use a rubber spatula to fold in the dark chocolate and pecans.

Using a 2 tablespoon cookie scoop, portion the dough onto a small parchment lined baking sheet. Freeze the cookie dough for 30 minutes.

Meanwhile, preheat the oven to 350 degrees F and line two large baking sheets with parchment paper.

Place the chilled cookie dough balls on the baking sheet about 2 inches apart. Top each of them with more chocolate and pecans, if desired. Bake the cookies for about 8 minutes until barely golden on the edges.

Once the cookies come out of the oven, immediately use a round cookie cutter or glass to scoot the edges in and make them perfectly round.

Allow them to cool for a few minutes on the baking sheet, then sprinkle with flaky sea salt and enjoy!