Use only a very dark unsweetened cocoa powder. I favor Hershey's Special Dark Cocoa powder. I do a couple of variations including pouring a can of sweetened condensed milk over the top of the batter once in the pan and then sprinkling 2/3 cup of coconut on top of that before baking. Last night I put toasted walnuts in them. Everyone loves these homemade brownies because they are moist and so chocolatey!