We prefer dark, unsweetened, Dutch process cocoa powders for a small brownie batch. We love this recipe with King Arthur's Double Dark Cocoa Powder or Black Cocoa Powder. You can use a lighter cocoa powder (like Hershey's, Nestle, or ALDI brands), but the brownies won't be as rich and complex, and they'll be a bit lighter in color (they'll still taste great, though!)