These came about because we decided to make brownies, but I couldn't be arsed to deal with melting chocolate so wanted to make them with Cocoa only. Was a little bit worried that it'd result in a loss of volume though, so wanted to add something to bulk it back out.
My cake pan is actually too large for this recipe, and my mixing bowl too small to make more in one go. So, rather than buying and storing yet more kit, the approach we tend to take is to make one set of the mix, measure out new ingredients and then make another set. This means you can do layered stuff like (in the pic) having a darker layer with just raspberries in it beneath a lighter layer with raspberry and white chocolate
The volume loss of not having the chocolate isn't actually that great though (the coca increase offsets it quite well), so you can just as easily leave out the raspberries and white chocolate if you prefer straight brownies.
Everyone loves chocolate brownies...