Brown the Butter: Melt unsalted butter in a light-colored saucepan over medium heat. Swirl gently as it foams and crackles. After 4 to 5 minutes, golden-brown specks will appear with a rich, nutty aroma. Immediately pour into a heatproof bowl and let cool to lukewarm (about 15 minutes).

Whisk Wet Ingredients: In a large bowl, whisk cooled brown butter with dark brown sugar and granulated sugar until well combined. Add eggs and vanilla extract; whisk vigorously for 1 to 2 minutes until glossy and slightly ribbon-like.

Fold Dry Ingredients: In a separate bowl, whisk together flour, baking soda, and fine sea salt. Gently fold dry ingredients into wet mixture with a rubber spatula just until combined, leaving a few flour streaks. Fold in chopped dark chocolate chunks, reserving a few for the tops.

Chill the Dough: Cover dough with plastic wrap and refrigerate for 30 to 45 minutes to allow flour hydration and let rich brown butter flavors meld.

Scoop & Bake: Preheat oven to 350°F (175°C) and line two large baking sheets with parchment paper. Scoop 3-tablespoon mounds (about 55g each) onto baking sheets, spacing 3 inches apart. Press reserved chocolate pieces on top. Bake for 10 to 12 minutes until edges are golden and set but centers remain soft.

Pan-Bang & Finish: Immediately upon pulling from oven, gently swirl a large round cookie cutter or glass around each cookie to shape into perfect rounds, then sprinkle generously with flaky Maldon sea salt. Cool on the baking sheet for 10 minutes before transferring to a wire rack.