1. Mix milk and vinegar. Melt the chocolate. Sieve flour, cocoa and soda into a bowl. Add margarine, sugar, eggs and half the milk mixture and beat well.
2. Add the melted chocolate and remaining milk. Beat until smooth. Transfer to 8" round cake tin which has been greased & lined. Bake in a preheated oven at 325°F,160°C,Gas Mark 3 for 11/2 hours approx. When cake is cold, split in half & use half the filling to sandwich cake. With remaining filling, completely cover cake & decorate to your choice.

To make filling

1. Put sugar & evaporated milk into a saucepan. Stir and bring to the boil, then simmer for 5 mins. Remove from heat. Add the broken chocolate & stir until melted. Repeat with margarine. Pour into a bowl & leave in fridge until it thickens