Can I use cocoa powder instead of dark chocolate for Nigella's Brownie recipe? If yes then what should be the quantity of fat and sugar which needs to be added or adjusted so that the same texture and sweetness can be maintained? Also I have cast iron, ceramic and aluminium foil pans. So I was wondering which is the best pan to bake the brownie for the best result?
Nigella's Brownies recipe gets its rich flavour from the melted dark (bittersweet) chocolate that is used in the cake batter. Unfortunately we can't recommend using cocoa powder as a substitute as the texture and flavour will be different and it is difficult to adjust the fat and sugar quantities accurately. We would suggest that you look at Nigella's Bacon Brownies recipe instead as this uses cocoa powder in the batter. The bacon gives the brownies an extra sweet and salty edge but you could replace this with about 100g walnut pieces.
The Bacon Brownie recipe also uses an aluminium foil pan so the baking time would be about right for this type of pan. Ovens vary, so check the brownies after the shorter baking time to make sure that they don't overcook. We wouldn't recommend baking the brownies in a cast iron pan as these retain heat for a long time and the brownies could overcook after they have been removed from the oven, due to the residual heat of the pan. A ceramic pan can also retain heat, so we would prefer to use an aluminium foil or metal baking pan.