01 - 
                Set your oven to 160ºC (320ºF) with a fan or 170ºC (338ºF) for conventional heating. Prepare a baking tray by lining it with parchment paper.
              
              
              
                02 - 
                In a heatproof bowl, combine the chopped dark chocolate and butter. Place this bowl over a pan of simmering water, ensuring the bottom doesn't touch the water. Stir until melted and combined. Stir in vanilla extract.
              
              
              
                03 - 
                In a separate medium bowl, use an electric hand whisk on high speed to beat the caster sugar, light brown sugar, and eggs until very light, thick, and fluffy.
              
              
              
                04 - 
                In another bowl, sift together the flour, cocoa powder, baking powder, chocolate chips, and salt.
              
              
              
                05 - 
                Gradually fold the melted chocolate mixture into the whipped eggs and sugars. Then carefully fold in the dry ingredients until just combined.
              
              
              
                06 - 
                Scoop tablespoons of batter onto the prepared baking tray, spacing well apart. Bake for 12-14 minutes, until set and crackly on top.
              
              
              
                07 - 
                Remove from oven and optionally sprinkle with sea salt. Let cool on the baking tray for 10 minutes before transferring to a cooling rack.