Preheat the oven to 180C (160C fan forced). Grease and line the base of a 22cm or 23cm cake pan.
Sift the dry ingredients together into bowl and mix to combine. Make three deep wells in the mixture with the base of a measuring cup or spoon. Pour the oil into one well, vinegar into the second and vanilla into the third. Pour cold water over the top and stir well with a fork or whisk. Pour into the pan.
Bake for 1 hour, 10 minutes, or until a skewer inserted into the centre of the cake come out clean with only some moist crumbs sticking to it. Allow to cool for 10 minutes, then gently remove from the pan onto a cooking rack. Cool completely.
For the Milk Chocolate Ganache:
Heat the cream in a small saucepan. Remove from the heat and stir in the chocolate until it has melted and the mixture is smooth. Spread over the cooled cake or refrigerate until it has thickened and then spread over the cake.
Store any leftover cake in an airtight container for up to two days.