01 - Preheat oven to 350°F. Line two baking sheets with parchment paper.
02 - Set a heatproof bowl over a pot of simmering water. Melt chopped dark chocolate and butter together, stirring until smooth. Remove from heat and let cool slightly.
03 - In a medium bowl, whisk together flour, cocoa powder, baking powder, and sea salt until well blended.
04 - In a large bowl, whisk granulated sugar, brown sugar, eggs, and vanilla extract until pale and thick, about 2–3 minutes.
05 - Pour melted chocolate mixture into egg mixture. Whisk until fully combined and uniform.
06 - Fold dry ingredients into chocolate mixture using a spatula until just incorporated. Do not overmix.
07 - Gently fold chocolate chips into dough until evenly distributed.
08 - Using a medium cookie scoop or two spoons, drop heaping tablespoons of dough onto prepared baking sheets, spacing about 2 inches apart.
09 - Sprinkle flaky sea salt over dough mounds if desired.
10 - Bake for 10–12 minutes until tops are shiny and cracked but centers remain soft.
11 - Let cookies cool on baking sheets for 10 minutes, then transfer to wire rack to cool completely.