Preheat the oven to 180°C (350°F). Grease a 9 x 13-inch pan and set aside.
In a large mixing bowl, combine all the cake ingredients and mix well until combined. Transfer into the greased pan.
In a separate bowl, combine the fudge sauce ingredients, except for the hot water. Sprinkle the sugar/cocoa mixture over the top of the cake.
Gently pour the hot water over the top of the cake. Do not mix or whisk it.
Bake the pudding cake for 35-40 minutes, or until the top is just done.
Remove from the oven and let cool for 15 minutes before serving.