Preheat oven to 350℉
In a large bowl, mix together sugar, flour, cocoa, milk, butter, and vanilla.
Grease a baking dish, 11x7 or 9x13. I prefer the smaller size pan to make thicker cobbler.
Pour the base mixture into the greased baking dish and spread evenly across the bottom of the pan.
In the same bowl, mix together your topping mixture. That's your sugar, brown sugar, and cocoa powder.
Using your hands, spread the topping mixture over the base mixture in your pan. Careful not to stir or mix it in. You want it spread evenly across the top of your base but not incorporated.
After you have the topping on the base, now take your hot water and pour it evenly on top. Careful again not to mix! You want everything in layers.
Bake in the preheated 350° oven for 40 minutes.
Your all done! You can serve hot or cold however you like it best! My favorite is hot with homemade ice cream! Enjoy!