Preheat your oven to 160°C (320°F, fan) or 170°C (338°F, conventional). Line a baking tray with parchment paper.

Melt chopped dark chocolate and butter in a heatproof bowl over simmering water until smooth. Cool slightly, then mix in vanilla extract.

Whisk together room temperature eggs, caster sugar, and demerara sugar until light and fluffy, about 5 minutes.

Sift together plain flour, cocoa powder, baking powder, and salt in another bowl. Mix in chocolate chips.

Fold the melted chocolate mixture into the whipped egg mixture until just combined. Add dry ingredients and fold carefully.

Using a cookie scoop, drop batter onto prepared baking tray, leaving space between each. Bake for 12-14 minutes.

Cool on the tray for about 10 minutes before transferring to a wire rack to cool completely.