I'm sure dutch process cocoa would enhance them but I used bulk unsweetened cocoa that I purchased at Sahadi's and was perfectly happy with my results. I also used the microwave for the second step of combining the butter, cocoa and sugar rather than a double boiler. It took a mere two minutes rather than waiting for water to boil and standing over the heat stirring and, in my case since I don't own a double boiler, struggling to hold two random pots at just the right angle.
I highly recommend this recipe. If you want to mix things up heating up a brownie and serving it with mint chocolate chip ice cream or crumbling an aged brownie into ricotta cheese with some almonds.
By the way, I'm experiencing the great outdoors in Big Sky Country i.e. Montana and Canada 8/13 to 8/24, so any responses will come when I return. Thank you for your patience and wish me luck seeing a moose with a rack.