Crush the Oreos, we used our hands to do so. You dont need to crush them into fine crumbs, medium-sized chunks are great.
Preheat an oven to 180c (350f) and prep a parchment paper-lined baking sheet. This step is crucial because it's important to put the batter in the oven immediately (for a crackly top).
In a small mixing bowl, add the butter and the dark chocolate. Melt completely in the microwave or on a ben Marie. There is no need to let this mixture cool.
Meanwhile add the eggs, kosher salt, brown sugar, and granulated sugar and mix with an electric hand mixer for exactly 4 minutes (set a timer).
Immediately add the chocolate mixture to the whipped egg mixture, add the cocoa powder (sift it) and mix with the electric hand mixer for about 30 seconds or until they are combined.
Sift the flour, and baking powder into the wet mixture and add the oreo chunks, and mix until just combined.
Immediately scoop the batter with an ice cream scoop or a cookie scoop onto a parchment-lined baking sheet.
Bake the cookies in a 180c (350f) preheated oven for 10-12 minutes or until the cookies have a crackly top.
Immediately top the cookies with more oreo chunks for decoration and extra texture.
Let the cookies cool for 5 minutes before removing them to chill on a cooling rack. Top with flakey salt (optional) and enjoy!