Preheat the oven to 180°C
Mix together all of the dry ingredients (flour, sugar, cocoa, bicarbonate of soda, and salt). Using a fork get rid of any lumps
Add all other ingredients (water, vanilla, oil and vinegar) and mix thoroughly
Pour into a lightly greased cake tin and bake until a knife comes out clean (about 25 mins)
Let cool on a rack before glazing
In a saucepan bring the milk, margarine, sugar and cocoa to a boil.
Reduce heat and simmer for 2 minutes stirring continuously
Remove from heat and keep stirring for 5 minutes. Sauce will thicken slightly giving a slight toffee taste.
Add Vanilla and stir together.
Spread on cake and let cool before serving