The melted chocolate and butter mixture must be COMPLETELY cooled before adding to the mixture otherwise it will cook the eggs. It will take around 30 minutes to cool to room temperature.
The eggs and sugar should be whisked until a trail of ribbons form when the whisk is pulled away. This will take 3-5 minutes.
You must use dark chocolate to get the chocolatey fudgy texture.
Cheap dark chocolate works fine for brownies. I used cheap dark chocolate with a 50% cocoa content and it worked fine.
The higher the cocoa content in the dark chocolate, the richer and fudgier the brownies will be.
Be careful not to knock any air out of the eggs and sugar- you need to carefully fold the ingredients in a figure of 8 motion.
All ovens vary, but the brownies will be done when the centre wobbles. You are also looking for moist crumbs when a skewer in inserted into the centre. If the skewer is still covered in raw batter, they are not yet done. If the skewer is clean, they are overbaked.
The brownies will continue to cook as they cool. Refrigerating them also helps them to set and makes them easier to cut.
Cool the brownies for 3-4 hours and then place in the fridge for at least 2 hours, preferably overnight for best results.
These brownies will last for 4-5 days in an airtight container.