This is one of those recipes where exact measurements may not work well. How dry the cake is, where you live, how many people you want to serve will change the proportions considerably. Use your instincts to know what works. This recipe is just a guideline to make the lamingtons.
You may also make a filling of your choice and layer two pieces of cake with it before dipping in chocolate. Or after dipping in chocolate! be creative and enjoy them anyway you like