Allyson's Dark Chocolate Tray Cake

Back in good ol' SA we have a supermarket chain called Pick'nPay. They have their own little cookery school - it's been going for some 20 years or more. Just like at Waitrose here, you can pick up a leaflet as you leave the store with some great recipes. Considering that these used to be photocopies, you'll have an idea of when last I took one. Today was our annual community Christmas day at church - when they throw the doors open to harrassed shoppers and exhausted parents - serve up lots of Xmas cheer, spicey apple drinks, and loads of home baking. I contributed with an all time CLASSIC which never fails : Allyson's Dark Chocolate Tray Cake. It's got lots of sugar, cocoa and buttermilk in it. And it is divine.
You bake it straight in a greased inch deep baking tray. You pour the icing on top (I did it while it was still warm). And it is moist and chocolatey and you can't go wrong. OK, I think I've sold it enough