Preparation

• Preheat the Oven: 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.
• Melt Chocolate and Butter: In a heatproof bowl, combine the chopped dark chocolate and butter. Place this bowl over a pan of simmering water, making sure the bottom of the bowl does not touch the water. Stir occasionally until melted and combined. Stir in the vanilla extract.
• Whip Eggs and Sugars: In a separate medium bowl, use an electric hand whisk on high speed to beat the caster sugar, demerara sugar, and eggs until very light and fluffy, about 5 minutes.
• Combine Dry Ingredients: In another bowl, sift together the flour, cocoa powder, baking powder, and salt, and then add the chocolate chips.
• Integrate Chocolate Mixture: Gradually fold the melted chocolate and butter mixture into the whipped eggs and sugars, stirring gently.
• Fold in Dry Ingredients: Carefully fold the dry ingredients into the wet mixture using a spatula until just combined.
• Bake the Brookies: Scoop tablespoons of batter onto the prepared baking tray, spacing them well apart. Bake for 12-14 minutes, or until set and crackly on top.
• Cool and Finish: Remove and sprinkle with sea salt if desired. Let cool on the tray for about 10 minutes before transferring to a cooling rack.