Preheat oven to 350F. Lightly butter an 8-cup baking dish.

Combine the flour, ½ cup white sugar, baking powder and salt in the bowl of a stand mixer with the paddle attachment.

Add the milk and vanilla, and stir until thick and smooth.
In a small bowl, mix the butter with 3 tablespoon of unsweetened cocoa until blended. Stir the cocoa mixture and chopped chocolate into the four mixture, until just combined.

Turn the cake mixture into the buttered baking dish.

In a small bowl combine ⅓ cup white sugar, brown sugar and 2 tablespoon of unsweetened cocoa. {If your're making this for a dinner party, stop here and wait unti just before serving dinner to complete these next steps. Put it in the oven to bake while you eat dinner, and it will be ready in time for dessert. }

Sprinkle the mixture evenly over the top of the pudding mixture. Do not combine it.

Carefully pour the water over the top of the sprinkled dry mixture, being careful not to combine it either. DO NOT STIR.

Bake in the centre of 350F oven for 25 to 30 minutes until the top of the cake is slightly glazed on top and the sauce is bubbling around the edges.

Serve hot with vanilla ice cream.