With the rack in the middle position, preheat the oven to 180 °C (350 °F). With the softened butter, generously butter a 2.5 litres (10 cups) Bundt or novelty-shaped pan. Sprinkle with a mixture of equal parts sugar and cocoa powder.
In a bowl, combine the dry ingredients. Set aside.
In another bowl, combine the chocolate and oil with an electric mixer. Add the eggs and beat until smooth. At low speed, add the milk alternately with the dry ingredients. Gradually add the boiling water and beat until smooth. Pour into the prepared pan. Bake for about 40 minutes or until a toothpick inserted in the centre of the cake comes out clean.
Let cool for about 15 minutes and unmould the cake by inverting it onto a wire rack. Let cool completely.
In a bowl, pour the hot cream over the chocolate. With a whisk, stir until the ganache is smooth. Add the butter and syrup and stir until smooth. Let cool until it thickens slightly. Drizzle over the cooled cake.