Preheat the Oven:

• Set oven to 160ºC (320ºF) with a fan or 170ºC (338ºF) for conventional heat.
• Line a baking tray with parchment paper.

2. Melt Chocolate and Butter:

• Combine chopped dark chocolate and butter in a heatproof bowl.
• Place the bowl over a pan of simmering water, ensuring the bowl’s base doesn’t touch the water.
• Stir occasionally until melted and smooth. Add vanilla extract and mix.

3. Whip Eggs and Sugars:

• In a medium bowl, use an electric whisk on high speed to beat caster sugar, demerara sugar, and eggs.
• Whisk until the mixture becomes thick, pale, and fluffy.

4. Mix Dry Ingredients:

• In another bowl, sift together flour, cocoa powder, baking powder, and salt.
• Stir in the chocolate chips.

5. Combine Wet and Dry Mixtures:

• Gently fold the melted chocolate mixture into the whipped eggs and sugars.
• Carefully fold in the dry ingredients with a spatula, mixing until just combined to avoid deflating the batter.

6. Bake the Brookies:

• Scoop tablespoon-sized amounts of batter onto the prepared baking tray, leaving space between for spreading.
• Bake for 12-14 minutes, or until the tops are set and crackly.

7. Cool and Serve:

• Optional: Sprinkle with sea salt immediately after baking for added flavor.
• Cool brookies on the baking tray for 10 minutes, then transfer to a wire rack to cool completely.