Melt Chocolate and Butter: Finely chop dark or bittersweet chocolate and place in a heatproof bowl over simmering water with unsalted butter until melted and smooth, about 5–7 minutes. Cool slightly.

Whisk Dry Ingredients: In a separate bowl, whisk together the all-purpose flour, Dutch process cocoa powder, baking powder, and salt. Set aside.

Beat Eggs and Sugar: Beat large eggs and brown sugar on high speed for 4–5 minutes until thick, pale, and fluffy.

Combine Mixtures: Fold in the cooled chocolate and butter into the egg and sugar mixture, then add dry ingredients in two additions until just combined.

Chill the Dough: Cover the mixing bowl with plastic wrap and refrigerate for 20-30 minutes.

Preheat Oven: Preheat oven to 350°F (180°C) and line two baking sheets with parchment paper.

Scoop Dough: Use a cookie scoop to form balls of dough and place on the baking sheets 3 inches apart. Sprinkle flaked sea salt on top.

Bake Cookies: Bake in the oven for 10-12 minutes until puffed and crackly on top but slightly underdone in the center.

Cool: Let cookies sit on the baking sheet for at least 20 minutes before transferring to a wire rack to cool completely.