Preheat your oven to 350 degrees Fahrenheit. Line a large baking sheet (15 x 21 inches) with parchment paper. If you prefer shiny tops on all your cookies, opt for a large sheet rather than using two standard ones.

Melt the butter and chopped dark chocolate together, then set aside to cool slightly.

In a medium-sized bowl, whisk together the all-purpose flour, cocoa powder, salt, and baking powder. Set this dry mix aside.

In a large bowl, beat together the white sugar, brown sugar, eggs, and vanilla extract using an electric mixer for about 7 minutes. This step is crucial for creating that signature crinkly top when baking the cookies.

Mix in the melted chocolate and butter into the wet ingredients.

Add the dry ingredients to the wet mixture and mix until just combined. The dough will be soft.

Scoop the dough into 30 portions (using a 1 tablespoon capacity scoop) onto the prepared baking sheet, spacing them about 1 ½ inches apart. Don't worry about perfect scoops; they won't be your usual cookie dough balls. Work quickly to maintain the shiny, crackly tops.

Bake the cookies for 11-12 minutes until the tops crack. If you desire a more circular shape, use a circular cookie cutter around the edges as soon as they come out of the oven.

Let the cookies cool on the baking sheet for 5 minutes, then transfer them to a wire rack to cool completely. Sprinkle with flaky sea salt before serving.