Grease a shallow tin. Mix the sugar, marg and flour together with your hands. When its ready (breadcrumb-y), add the egg, then stir in the blackberries- a few at a time.
At this point, it will look like a complete failure: a little soggy perhaps, and an alarming colour. Don't panic!
Pop it into the tin and cook quite gently (190 degrees-ish) for a while (45 minutes-ish). Its a little vague, because the cooking time varies with the amount of blackberries you add- ie, how wet the mixture is. But this isn't the sort of recipe to be worried about accuracy and measurements. This is where my mum and I differ- she goes for a few blackberries, for flavour, and I tend to chuck them all in, in the excitement, and keep vigil by the oven for a very long time- until a skewer comes out fairly clean. A little juicy squishyness is ok- as long as it has firmed a bit, and you're satisfied that the egg is cooked, and the cake is 'done'. Both of our cakes are lovely, but mine feels more decadent, and I will readily accept my mum's point that my version needs to be eaten quickly or refridgerated, and hers doesn't. Thats fine- they never last very long in my house anyway. She also keeps back 2oz of sugar to sprinkle on the top just before she bakes, so that she has a firm topping.
Its especially lovely served warm, and also nicest if you can resist the urge to beat the mixture into oblivion- the plain cakey taste in amongst the blackberries- and the contrasts of colour between the two, (almost a marble effect) are one of the nicest aspects. Its also a good idea to keep some fruits back, and pop them in 'whole' once the mixture is in the tin, ready for the oven. Its such a fun cake! And perhaps all the nicer, as it is a seasonal one, and something to look forward to, just a couple of times a year. I can't take the credit for this recipe- it initially came from the very lovely Mrs ABC, who always provided the most popular cakes at the bakey Children's Society Sale back home.
Enjoy. Before the blackberry picking, I'm going to nurse my cold and rest my sinusy-head, which has lingered a week- which is the main cause of my absense this time! Sorry about that... I also need to talk nicely to my washing machine and my digi-box as they have both had a rebellious moment today. Things come in threes don't they... I'll let you know what breaks down next!