Preheat your oven to 350°F (175°C). In a heatproof bowl, combine dark chocolate and butter, then set it over a saucepan with simmering water, stirring gently until melted and smooth. Remove from heat to cool slightly.

In a mixing bowl, whisk together eggs and both types of sugar until pale yellow and thickened (about 2-3 minutes). Gradually pour in the melted chocolate mixture, stirring to combine.

In another bowl, whisk plain flour, cocoa powder, and a pinch of salt. Gradually add this dry mixture to the chocolate mixture, stirring gently until just combined; it will be thick and slightly lumpy.

Gently fold in your chocolate chips using a spatula, ensuring not to overmix. The dough should remain thick and gooey.

Drop spoonfuls of dough onto a lined baking sheet, leaving space between each mound. Bake for 12-14 minutes until edges are set and centers look slightly soft.

Allow brookies to cool on the baking sheet for 5 minutes before transferring to a wire rack. Serve warm or at room temperature.