01 - Preheat oven to 350°F. Line two baking sheets with parchment paper.
02 - Set a heatproof bowl over a pot of simmering water to create a double boiler. Add chopped dark chocolate and cubed butter. Stir continuously until completely melted and smooth. Remove from heat and allow to cool slightly.
03 - In a medium bowl, whisk together all-purpose flour, cocoa powder, baking powder, and fine sea salt until evenly distributed.
04 - In a large bowl, whisk granulated sugar, brown sugar, eggs, and vanilla extract vigorously for 2-3 minutes until mixture becomes pale in color and thickened in consistency.
05 - Pour the cooled melted chocolate mixture into the egg mixture. Whisk until fully combined and uniform in color.
06 - Add the dry ingredient mixture to the wet ingredients. Using a spatula, fold gently until just incorporated. Be careful not to overmix as this will affect the final texture.
07 - Gently fold in the chocolate chips until evenly distributed throughout the dough.
08 - Using a medium cookie scoop or two spoons, drop heaping tablespoons of dough onto the prepared baking sheets. Space cookies approximately 2 inches apart to allow for spreading.
09 - Lightly sprinkle flaky sea salt over the tops of each cookie dough mound if desired.
10 - Bake for 10-12 minutes. The tops should appear shiny and cracked while the centers remain slightly soft. Remove from oven when edges are set.
11 - Allow cookies to cool on the baking sheets for 10 minutes to set. Transfer to a wire rack and cool completely before serving.