Preheat oven to 180ºC (160ºC fan forced). Grease and line a square pan with baking paper.

In a microwave-safe bowl, add chocolate and butter. Microwave in increments of 30 seconds, stirring in between, until combined and glossy. 

Remove from heat and allow to cool slightly. 

Stir in eggs, followed by castor sugar, brown sugar, vanilla, flour, cocoa powder and salt.

Pour batter into your prepared tin. Bake for 30-35 minutes, or until an inserted skewer comes out with some wet crumbs. Don’t overcook! 

Allow to cool completely before slicing and serving.