I bought a little cook book when I toured New Zealand a few years ago. It was one produced by wives in the area - mainly farmers wives as it was a farming area. It really is so easy to do.
150grms plain chocolate
150grms dark brown sugar - I use whatever I have, muscavado, demerara, light brown
150grms block margarine or butter - NOT soft marge
175grms plain flour
4tbs (heaped) cocoa powder
2 tsp baking powder
3 mashed bananas - big ones if you can get them
Melt the chocolate, sugar, and butter over a very low heat, keep stirring to mix it all together - leave to cool
Sieve all the dry ingredients together, then mix in everything else.
I cook mine in a 2lb loaf tin lined with a paper case, but you can use a cake tin etc which should be greased.
Cook for about an hour at 150c. I like to cook mine so that it is just a little bit soft when you test it with a skewer, as it cools it is really moist.
It rises well and freezes wonderfully. I like it as cake or sliced as a pudding with ice cream, cream, yoghurt or custard.
I have cooked this substiting the juice and zest from an orange and it was lovely too.
Give it a go - you'll love it.