Mum's chocolate cake

For those of you who were in London for Harry Potter and were asking about the recipe for the chocolate cake.

4ozs  Margarine
3ozs  Sugar
1Tbsp Cocoa
1 Cup Raisins
1 Egg
8ozs Digestive Biscuits (Crushed to crumbs – a potato masher works really well)

4oz Cooking Chocolate (to cover)

Cooking equipment needed
Large saucepan
Swiss roll tin

Melt margarine in saucepan on a low heat, then add sugar. Wait until it dissolves, then add the cocoa and raisins. Allow to boil for about a minute, until the cocoa thickens.
Remove from heat and allow to cool for about 20-30mins.
Then add the egg, making sure the mixture is cool enough to prevent the white from solidifying. Stir the mixture thoroughly.
Add the biscuits, stirring until completely mixed in. The mixture should have a thick but still spreadable consistency.

Spread the mixture out evenly in the swiss roll tin. Leave to set.

Melt the chocolate (in microwave or over boiling water) and spread evenly over the cake. When the chocolate in nearly set, mark cutting lines in squares. (So chocolate doesn't crack when finally cut.)

Have fun!