This is a good cake that I have made frequently. I managed to find it on-line rather than having to copy it out from my own copy of the "I Hate to Cook Book". It really does come out rich and moist and chocolatey :) The measures are Amercian ones - 1 cup = 8 fl.oz
I choose to mix it in a separate bowl, so I don't find unmixed bits of flour when you turn the cake out - plus you get the bowl to lick out 
I've never bothered icing it - but melting After 8s in the way this blogger suggest is probably a quick and easy (and sinfully yummy ) way of doing it.
Anyway, here it is - it's called a "Cockeyed Cake":
"This is from the hallowed pages of the "I Hate To Cook Book" by Peg Bracken. It is amazingly simple, foolproof, and delicious. It has the advantage of making you feel that you are living dangerously. A recipe that contradicts all the rules of baking and succeeds every time is as good as a holiday.
* 1 1/2 cups flour
* 3 tbsp. cocoa
* 1 tsp. baking soda
* 1 cup sugar
* 1/2 tsp. salt
* 5 tbsp. cooking oil
* 1 tbsp. vinegar
* 1 tsp. vanilla
* 1 cup cold water
In bowl mix flour, cocoa, baking soda, sugar and salt. Put into a greased cake tin (about 9x9x2 inch). Now make three grooves in this dry mixture. Pour the oil into one, the vinegar into the next, and the vanilla into the next. Throw the cold water over it all and mix it all up with a wooden spoon leisurely. Just make sure all the flour is blended in. Bake at 350F for 30 minutes.
Icing:
Put 4 or 5 large chocolate covered peppermint patties on top and slip them under the broiler for 5 minutes. Wet a knife or spatula and smear the patties all over the top. This is sinfully easy and delicious too.