Preheat your oven to 180C/160C Fan and line a 9x9" baking tin with parchment paper!
Melt together your Dark Chocolate and Unsalted Butter until smooth in the microwave or in a bowl over a pan of simmering water. Leave to cool for a few minutes
Using an electric whisk/stand mixer, whisk your Eggs and Sugar together for 5 minutes or so on high speed, or until the mixture has doubled in volume, is alot paler, and leaves a trail for a few seconds when you lift the whisk out.
Pour in the chocolate/butter mix and fold through very carefully.
Add in the Flour and Cocoa Powder and fold through carefully again.
Add in your frozen chunks of Mars Bar and chocolate chips and fold in. Pour the mixture into the tin and bake in the oven for 25-30+ minutes.
Leave to cool in the tin, and then enjoy!
To decorate your brownies if you fancy it... melt your chocolate and drizzle over the brownies, and add pieces of Mars Bar to each one! Set in the fridge, then chop up and enjoy!
Please try and freeze the Mars Bar first as it'll work so much better!
These will last for one week+!
You can use caster sugar instead of the brown sugar, the brown sugar just works really well for the Mars Bar theme!
If your brownies are taking much longer than stated to bake, your oven may have been the wrong temperature, or you over mixed your batter. Keep adding on 5 minutes till they're done and cover with foil if need be!