Preheat the over to 180°C and leave the eggs to cool to room temperature. Sift the flour and cocoa powder.

Combine the butter and chocolate in a microwave-safe bowl and heat it up until melted, about 1 minute.

Add the granulated sugar and mix. Then, add the eggs one by one and mix. Finally, add the salt and vanilla essence and mix.

Transfer the batter to a baking tray/mold and bake for 20 minutes. Cut into bite size squares to serve.