Preheat the Oven
Preheat your oven to 160ºC (320ºF) fan or 170ºC (338ºF) conventional.
Line a baking tray with parchment paper.
Melt the Chocolate and Butter
Combine the chopped dark chocolate and butter in a heatproof bowl.
Place the bowl over a pan of simmering water, making sure the bowl doesn't touch the water.
Stir occasionally until smooth and melted.
Remove from heat and stir in the vanilla extract.
Whip the Eggs and Sugars
In a separate medium bowl, beat the eggs, caster sugar, and demerara sugar with an electric whisk on high speed.
Whisk until the mixture is very light, thick, and fluffy.
Combine Dry Ingredients
In another bowl, sift together the flour, cocoa powder, baking powder, salt, and chocolate chips.
Mix the Wet and Dry Ingredients
Gently fold the melted chocolate mixture into the whipped eggs and sugars, maintaining the airy texture.
Fold in the dry ingredients using a spatula just until combined—do not overmix.
Bake the Brookies
Scoop tablespoons of batter onto the lined tray, leaving space between each for spreading.
Bake for 12–14 minutes, or until the tops are crackly and set.
Cool and Serve
Remove from oven and optionally sprinkle with sea salt.
Let the brookies cool on the tray for 10 minutes, then transfer to a wire rack to cool completely.
Notes
If melting chocolate in the microwave, use short bursts and stir in between to avoid overheating.
The egg and sugar mixture should be thick enough to leave a ribbon trail when lifted with a whisk.
Use a cookie scoop for uniform brookie sizes.
Allowing them to cool on the tray helps them set without falling apart.