Preheat your oven to 160°C (320°F) for fan-assisted baking or 170°C (338°F) for conventional ovens.

Line a baking tray with parchment paper to prevent the brookies from sticking.

Melt dark chocolate and butter in a heat-proof bowl over a pot of simmering water, stirring until smooth.

Whip eggs, caster sugar, and demerara sugar together until light and fluffy.

Sift plain flour, cocoa powder, baking powder, and salt into a bowl, mixing in chocolate chips if using.

Gently fold the melted chocolate mixture into the whipped egg mixture, then fold in the dry ingredients until just mixed.

Dollop the batter onto the prepared baking tray, spacing them about 2 inches apart.

Bake for 12-14 minutes until edges are set but centers remain soft.

Let brookies cool on the tray for 10 minutes before transferring to a wire rack.