Grease and flour two 8 1/2 inch round sandwich tins and line the bottom of each with greaseproof paper (baking parchment?
).
Sift the flour, bicarbonate of soda and the two types of sugar into a bowl and make a well in the centre.
place the water, cocoa powder and butter in a small saucepan and stir over a medium heat until the butter melts and the mixture is smooth- don't allow the mixture to boil though.
Remove from the heat and stir in the vanilla.
Add the vinegar to the cream and stir into the flour/sugar mixture.
Add the cocoa mixture and eggs- there should be no more cake ingredients left- and whisk together until smooth.
Divide the mixture equally between the two tins and bake for 20-25 minutes until until the cakes have risen and are firm but springy to the touch.
Remove rom the tins& place on wire racks to cool.
For the filling:.
Put the chocolate& water into a small saucepan& melt over a low heat, stirring continuously, until smooth- set this mixture aside for a moment.
Put the caster sugar, cream and butter into another saucepan& heat over a moderate heat for 4 to 5 minutes, stirring continuously until the spoon will leave a trail in the mixture.
Remove from the heat& stir in the chocolate mixture and the vanilla.
Allow to cool, stirring occasionally& then place in a fridge until cold.
Sandwich the two cakes together with the filling and leave on a rack over a tray.
To ice the cake:.
Put the remaining chocolate in a small saucepan with the butter and the water.
Heat, whilst stirring continuously, until the chocolate melts& the mixture becomes smooth and will coat the back of a spoon- do NOT overheat.
Pour the icing over the top of the cake and then chill until set.